This is smart play.
Dungeon restocking/tactics adjustment helps but maybe is not The Total Solution (TM).
Here's something I'm doing. It's for a 4e game but should be broadly applicable:
WHEN THEY REGAIN THEIR DAILY RESOURCES, MAKE A HARD MOVE.
A "hard move" is a term from Apocalypse World. It refers to the dreaded and irrevocable consequence of an explicit or implicit threat.
In combat, a hard move is injury/death.
In addiction narratives, a hard move is relapse.
In relationship narratives, a hard move is they're seeing someone else.
In a thieves guild game, a hard move is a raid on your HQ or the arrest of one of your members.
So find out what your hard moves might look like and tell the players that this metastructure is in effect.
If they care about the consequences of your hard moves, the problem is resolved.
Sure, they can nova and drop the mic, but then their significant other gets kidnapped.
Upside: something interesting is always happening, and things get more complicated.
So, if the 15 minute day is a problem for you, here you go.
This has the side benefit of addressing an issue in 4e: by default, it doesn't matter how well the party fights as long as they win.
With this rule in effect, though, fighting well means you lose fewer hp, which means your surges will last longer, which means you can go longer between extended rests, which means you limit the GM's hard moves.