Is leveling up mandatory?

Question

In D&D 3.5e, being behind in levels compared to the party grants the relevant characters more experience per encounter. Intuitively, this is because the encounter is relatively harder for them and it works as a catch-up mechanism.

Now, as experience can be spent on other things than gaining levels, the question was raised in my group whether gaining a level is mandatory when the relevant experience thresholds are reached. The implicit idea being that by delaying gaining levels, characters can get a much bigger power boost at once when they actually need it.

One player in particular worked out the math insofar that he could jump from level 12 to 17 while the rest of the party sits at 15.

The arguments make sense, but I am not entirely sure how to handle this idea. Staying behind in level deliberately seems detrimental to the experience of not just the player but also the rest of the group - who will be dragging along effectively dead weight for a while after which said dead weight will outshine all of them.

1. Is this a legal interpretation of experience and level rules?
2. Am I wrong in assuming that allowing this would be a bad thing?
3. How can I encourage players NOT to do this, even if it is by all accounts legal? I still want to allow item crafting and 'expensive' spellcasting.

Answer 1

You can't refuse to level up...

From the Players Handbook, "Experience and levels" p 58:

Advancing a Level: When your character’s XP total reaches at least the minimum XP needed for a new character level (see Table 3–2), he or she “goes up a level.”

(emphasis mine) That's not something that you can choose to do or not. As soon as you reach the requirements, you're considered to be of the new level you reached. It's the same thing as aging. You can't decide to remain at 12 years old for six years, then immediately become 18 years old.

Mechanically, that would probably break the game. The players would face encounters increasingly difficult, gaining increasingly more XP. He would potentially gain even more levels than what he expects. That seems pretty unfair to the others players, as they would have to carry him during the time he saves his points.

Furthermore, does he expect to show in front of the BBEG (lv 17, to accommodate the 15-th party level) and then snap his fingers to magically upgrade to level 17 and fight him on equal ground? That doesn't seems fair either, for the players and you.

... unless some very specific circumstances.

The very first entry about creation of magic items and XP cost is located in the Players Handbook, page 88:

XP Cost: Power and energy that the spellcaster would normally have is expended when making a magic item. The XP cost equals 1/25 the cost of the item in gold pieces (see the Dungeon Master’s Guide for item costs). A character cannot spend so much XP on an item that he or she loses a level. However, upon gaining enough XP to attain a new level, he or she can immediately expend XP on creating an item rather than keeping the XP to advance a level

So, you can delay your progression, but not choose to stop it, and under specifics circumstances (e.g: being able to craft magic items, and deciding, when you hit the requirements, to craft an item instead). It does not allow you to voluntarily lose a level by spending too much XP, nor does it not allow you to save it. You gain it, you spend it on either, but you don't have a magical pouch of XP somewhere. An "option" to lose a level, is for a wizard to get his familiar killed. The traumatism cause a XP loss, that can be halved on a saving throw (so not the loss is not done voluntarily). You can not "traumatize" yourself by crafting magicals items, as RAW.

Furthermore...

As pointed by Fectin, the section "Experience and levels - Advancing a level" mention a case where you can't access a level:

A character can advance only one level at a time. If, (...) a character’s XP reward from a single adventure would be enough to advance two or more levels at once, he or she instead advances one level and gains just enough XP to be 1 XP short of the next level. Any excess experience points are not retained.

From what I understand, even in this case, you don't save XP, you merely get a level and the experience needed to get to the following minus one. So you level up. And the additionnal experience is lost. So you're twice as disappointed. No delay, no savings.

Answer 2

Sort of.

Leveling up is not strictly mandatory. See e.g. the description of XP costs under spell components. I've also seen a similar caveat for item crafting, but couldn't find it quickly.

However, note also that you cannot accumulate enough XP to level twice (see PHB P.58, "Advancing A Level"). Instead, your experience is set at one less than the amount required for the second level gain (eg if you are third level, the most XP you could accumulate is 9,999, because 10,000 would put you at fifth level).

So yes: you can delay leveling in at least some circumstances, but no: it's not the crazy springboard your player hoped for.

Answer 3

Is this a legal interpretation of experience and level rules?

Nyakouai's answer does an excellent job of answering this particular part of your question, so intead of needlessly rehashing the same points I will simply refer to that answer.

Am I wrong in assuming that allowing this would be a bad thing?

No, you're not wrong. Setting aside the fact that this would alienate the other players, this dramatically increases the headache and workload associated with being the DM of the game, which is already a pretty thankless job. Just designing one encounter that would challenge a 15th level party but not annihilate a 12th level character would be a monumental undertaking. Keep in mind that 15th level full casters have access to 8th level spells, while 12th level full casters still top out at only 6th level spells. That alone is a huge power disparity. And that same 12th level full caster expects to suddenly jump to being able to cast 9th level spells at 17th level? If you can be persuaded to allow something like that, then I have a lovely bridge in China I'd love to sell you...

How can I encourage players NOT to do this, even if it is by all accounts legal? I still want to allow item crafting and 'expensive' spellcasting.

You don't need to discourage anything. Remember that you are in charge. It is your responsibility as the DM to make the game fair and balanced, and this would fall under the very definition of an unbalanced system. Even if it were a legal tactic within the rules, Rule Zero empowers you to simply say no. The only time I would personally allow a player to "delay" levelling up a character that possesses the requisite amount of XP to advance (assuming he does not intend to immediately spend that XP on a crafting project or a spell with an XP component) would be if the player wanted to advance in a class that they are barred from advancing temporarily. For example, a player wanting to take a level of Monk but can't because his character's alignment has shifted to non-lawful. I'd give him time to shift his alignment back to where it needs to be, but I would consider him to have "levelled up" for the purposes of encounter design and he would continue to gain XP toward the next following level as normal at the same rate as everyone else.

Answer 4

What I've always done to discourage this kind of activity is a few things:

First, their level, for the purposes of determining how much experience they receive from a session, is based on their experience point total. They chose not to actively level-up? They are hamstringing themselves.

Next, players could go into a sort of experience point-debt. At the end of the session, after experience was rewarded for the session, they had to settle their debt. If your total came out to be less than what you needed for your current level, you had an appropriate number of negative-levels applied until you could settle your debt. These negative levels would never kill the player (like those imposed by undead and etc), but they also could not be removed in any way, except when the player could settle the debt at end of session.

Finally, the players could put some of their experience points into a pool, for use of making items, spellcasting, and etc. These experience points were no longer considered experience for calculating their level, but also, these points could not be withdrawn for the purposes of leveling. Even non-spellcasters could donate to this pool, to help ease the experience costs for things like that. If a PC permanently died/withdrew from the group/etc, then they would take a proportionate amount with them. NPC henchmen/hirelings could do this too, however they would always demand 5-10g per experience point donated, above and beyond their typical payment/share of loot.

Because my game sessions were typically 12-16 hour affairs, I never imposed the 1-level-per-session rule.

Answer 5

If you allow it, and I personally wouldn't, once he is 17th level while the party is still 15th level, he will gain XP slower because of the same rule that allowed him to get more XP before. So, as time goes by the levels would then balance back out.

One or two levels one way or the other won't really unbalance the party greatly. The CR of the monsters isn't going to cause mayhem with such a small gap.

These rules were really made to help the party stay balanced, not as a trick for min/maxers to abuse. Players should be encouraged to think about what's best for the whole party, not just themselves. You are a team, so help each other rather than competing.

Good luck!