Can you usefully have two Boots of Speed enchantments on the same item?

In Pathfinder, the wondrous item crafting rules say that you can put additional effects onto a single item of a particular item slot at an additional 50% cost. I've also heard it said that weapons can have (for example) multiple flaming enchantments, each of which proc for 1d6 fire damage on a hit, so there doesn't appear to be a general rule against duplicate magical effects on a single item.

My query is: can I have a single feet-slot item empowered with two Boots of Speed enchantments and expect any sort of improved performance?

I understand that haste effects do not stack. I'm wondering if I could activate those enchantments separately, effectively providing twenty rounds of haste per day instead of the usual ten. Or would both instances always activate at the same time, giving me the usual ten rounds of haste and a 9000gp-shaped hole in my pocket?

I know I could just carry an extra pair with me. But so long as Paizo refuses to include the indispensable Greaves of Automatic Shoe-Swapping +1 in any upcoming splatbooks, that seems appallingly inelegant (and inconvenient for expensively piling on additional effects).

• Welcome to the site! Take the tour. A great, practical, and interesting first question. Thank you for participating and have fun! – Hey I Can Chan Sep 13 '17 at 23:05

In this case it makes more sense to modify the effect than it does to try and stack multiple copies of itself. Boots of Speed are a CL10 item and they offer ten rounds of haste per day because Haste cast at CL10 has a duration of ten rounds. Make them a CL20 item, and that'd translate to 20 rounds of haste instead.

When it comes to the price, the working for the original item is:

Spell Level (3)
* Caster Level (10)
* 2,000gp (use-activated effect)
/ 5 ("1" charge per day)
= 12,000gp

If you make that CL20 instead, you increase the base cost to 24,000gp, or 12k to craft. You could achieve the same effect for the same cost by calling it two charges per day for a total of 20 rounds, instead - but making the item CL20 instead increases its resistance to magical interference by others.

I am guessing your character is not a 20th level caster. Luckily, as per the sidebar on the SRD, no part of the magic item crafting rules actually requires the crafter to meet an item's CL; you can create your item at whatever CL you like, as long as it's high enough to cast the required spells and you can afford the cost.

• I +1ed, but with some reservations. I thought hard about suggesting something similar, but then why do that when you can just make boots of extended speed ((spell level 3 modified to 4 × caster level 10 × 2,000 gp) / 5) for a mere 16,000 gp? And when that gets suggested, the DM gets angry, then the player gets frustrated, then somebody flips the table, and everybody hates each other for years. (I liked that the asker didn't seem to really want a custom item and was willing to pay the gp to keep his friends. ;-)) – Hey I Can Chan Sep 13 '17 at 23:19
• Ooh, that's clever. I was vaguely aware of creating items at different caster levels, though it didn't occur to me that it would work for me here. Though I had recently come under the impression that you had to add 5 to the crafting DC for every level short of the item's CL you were, with all the horrific consequences therein. Glad to see that is not the case! – Captain Skylock Sep 14 '17 at 3:28

A creator can't put the same weapon special ability—like flaming—on a weapon multiple times: "Weapons cannot possess the same special ability more than once." However, that's a rule specific such magic items. I'm unaware of any specific similar rule that prevents layering a wondrous item onto a wondrous item, even if they're identical wondrous items, especially if the intention is that their effects be employed sequentially rather than simultaneously. (A double portable hole—a portable apartment?—, for example, might see this GM balk.)

That said, as with any essentially custom magic item, ask your GM, but according to Adding New Abilities, spending 12,000 gp on the boots of speed then paying another 18,000 gp to add the effects of boots of speed to those boots of speed seems, to this GM, excessive—perhaps even indulgent—but nonetheless legit. I mean, you're not expecting to be twice as hasty; you just don't want to change your shoes. So this GM wouldn't stop you: if that's how you want to spend your money, that's your business.

Also, because you're spending 30,000 gp on these boots, this GM'd give you the the 20 rounds of haste per day that you want. This GM would not rule, for instance, that clicking together the heels of the boots activates simultaneously both pairs of virtual boots, causing the haste effects to overlap. Were that the case, this GM would've warned you that's what would happen beforehand and had you save your time and treasure… and if a GM does say that's what happens after your PCs bought such boots, I suggest you use your own real-life boots for what they're made for.

• We'll see how the GM feels when they see the diabolical nonsense I have planned for them. – Captain Skylock Sep 14 '17 at 3:36

Wondrous Items aren't modular like magic Weapons and Armor are. Magic weapon and armor properties (or "enchants", if you like) can be added to weapons or armor a la carte and there are specific pricing tables for these. Wondrous items on the other hand are not an exact science, and each GM need to evaluate them individually.

That being said, you cannot have 2 "Boots of Speed" enchantments on a pair of boots, but you could have an effect that can be activated twice per day (or some other number) instead of once per day. It would be a custom magic item, so you would need to clear it with your GM and find someone in-game to craft it for you.