Adventure pieces larger than the encounter
The 5 minute adventuring day is caused by the "unit" of D&D being the encounter. You finish a unit of D&D, then you are at loose ends until the next unit.
And laying down in the middle of an encounter and having a long or short rest is an obviously bad plan.
If your "pieces" of adventure that the PCs interact with are larger than a single encounter, then laying down in the middle of that piece should also be an obviously bad plan.
The Scene is what I call a bundle of encounters "between short rests". For whatever reason, once you start a Scene, taking a short rest somehow causes the Scene to "fail".
This can be because the Scene engaged with the PCs (and doesn't let them disengage), or it could be because the PCs learned about a problem and have not much more than an hour to solve it, or because the Scene reacts to being interacted with, and an hour break means that the Scene's reaction makes the situation worse for the PCs in whatever way.
Guards could set off alarms, or be noticed as missing. A group could respond to being attacked by picking up and moving away.
An easy, natural way to have a Scene is a relatively living dungeon, each room relatively isolated from each other, but in an hour period intrusion is noticed. Another is a running battle in the wilderness against allied foes, or in an environment where short rests are not plausible.
The breaks between encounters can be as short as 1-5 minutes in a Scene, or as long as 59 minutes. They can even be longer than an hour if short rests are otherwise implausible, like on a ship in a storm.
A good Scene budget is 2-5 medium encounters (For other difficulties Easy as 0.5, Hard as 1.5 and Deadly as 2.0). An Easy scene has 2 Medium, a Deadly scene has 5+. But adjust based on your PCs capabilities.
The Chapter is what I call a set of Scenes that would "fail" if you took a long rest before finishing them.
Chapters should have 2-5 Medium difficulty Scenes in them. (Easy count as 0.5, Hard 1.5, Deadly as 2.0), with again an Easy chapter is 2 Medium Scenes, Medium has 3, Hard has 4 medium scenes, and Deadly has 5+ medium Scenes.
This can be a clock (your PCs learn they have 24 hours to save the world!), the enemy responding to contact, or a difficulty in doing a long rest given the environment the Chapter is in.
From the DMG
"Chapter" and "Scene" above roughly mimics the "adventuring day" advice in the DMG, with ~2 short rests (hence ~3 scenes) and 7-9 medium encounters per day (I rounded up to 3 medium encounters per scene). It just divides it up slightly differently, and instead of using "total XP" builds things using pieces based on narrative structure. And as "sum of XP" is abstract, while "these encounters chain together" isn't, it can help build things.
The XP ratios of encounters in the DMG are 1:2:3:4 for easy:medium:hard:deadly (or pretty close). This lines up with 0.5:1:1.5:2 medium encounters ratio (I used the "medium" encounter as my unit).
An encampment of raiders. This is a Medium Chapter. It has 2 Easy and 2 Deadly scenes.
Scene 1 is a scout patrol. (Easy Scene)
- An Easy vanguard Encounter (0.5)
- Hard main patrol Encounter (1.5).
Scene 2 is a heavy raiding party sent out in response to the missing scout patrol. (Easy Scene)
- A single Deadly Encounter.
Scene 3 is the actual camp. (Deadly Scene)
- Hard Cavalry Encounter (1.5)
- Hard Infantry Encounter (1.5)
- Deadly Boss fight Encounter (2.0)
The area has an outer ring of scout patrols, an inner ring of heavy raiders, and the camp itself. Much of the force is actually out raiding or patrolling.
In response to enemy contact they'll start getting reinforcements from raiders further out, from their home base, and eventually pull out with their treasure.
Any treasure reward is in the main camp.
An eternal storm exists in a region the PCs want to cross. Crossing it requires a week of travel. There is an oasis half way. Short rests require 8 hours and require difficult checks to avoid exhaustion, and long rests are impossible.
Scene 1: Land sharks! Because everyone
hates loves land sharks.
Scene 2: Fey pranks on the wind
Scene 3: Find an Oasis. It is defended by hostiles. (LONG REST is your reward)
Note that additional hostiles will approach the Oasis if they PCs stick around. The PCs do get a day's grace.
- Scene 1: Trolls under a Bridge (and maybe some billy goats)
In the event of a retreat, another hostile power could occupy the bridge, and the Oasis is again occupied by reinforcements.
- Scene 2: The Destination. Some encounter they get as they leave the storm.
Set the difficulties to taste; this is just a narrative structure.
The key here is that "5 minute adventuring day" doesn't work; the PCs would have to withdraw out of the storm, losing possibly days.
"Gritty" can make it easy for you
Use "gritty rests". In it, short rests are always overnight, and long rests require a week rest (in a safe spot).
Scenes/Chapters are tied together by plot. And plot-wise, it is far easier to justify "you fail" a Scene when you wait a day than if you wait an hour, and a Chapter "you fail" if the PCs go back to base and wait a week.
(I'd allow downtime style activities to take place during long rests).
As a bonus, this causes wall-clock time to pass, allowing the world to evolve and downtime to occur naturally. A Chapter takes 3-7 days of adventuring and 7 days of rest (10-14 days). If it takes 3 Chapters to earn enough XP to gain a level, that is a bit more than 1 month per level.
So even without a narrative break or extra downtime, it now takes about 1.5 years to reach level 20, instead of a few weeks. You can now take your sandbox and plot out events that will happen (barring PCs preventing them) on an in-game wall calendar.
Stick "T2" scale events PC can respond to ~6 months after game start, "T3" ~1 year, and "T4" ~18 months out. Have foreshadowing of these events coming before they happen (ie, if the T2 event is an overthrow of a Kingdom, hints it is happening can be dropped in month 1-5). This is a bit of a meta-clock, sort of like "Star Control 2".
This may require calibrating your encounter difficulty; Scenes now contain entire adventuring days. And single issues that are larger than a Chapter can end up taking a narrative month or more to resolve.
Don't build your adventure (or sandbox content!) in "encounter" pieces. Build it in larger pieces. Tie the encounters within the larger piece together.
PCs are expected to defeat the larger pieces "in detail". If they don't, they are screwed.
Consider "gritty" rests to help with narrative pacing. Justifying taking a week off having no effect is harder than doing it