Sending my Party Up Against the Dungeon Boss (With Just a Short Rest)

 For the past few sessions, my D&D party (the one I DM) has been fighting their way through a laboratory where an evil biomancer has been committing terrible atrocities. This is set in Ravnica, and my arc-plot is that there's a conspiracy to convert Ravnica's massive population into Phyrexians, which the party is trying to stop.

Thus, the first really big dungeon of the campaign has them traveling into Teveshen Laboratories, a Simic facility that is run by the rogue merfolk biomancer Tiburnas Lo'Sogra. The party is level 10, and breached the facility, going from Simic Hybrids and Krases to now fighting true Phyrexian monsters (many are re-skins of things like Karrnathi Undead Soldiers and Banderhobbs, though a fair number are total homebrew creations.)

It's the most arduous march of dangers I've put any party through, and while they opted to take a short rest at the beginning of tonight's session, I'm actually a little worried whether it was enough (the Barbarian is out of Rages, for example.)

Having first gotten into D&D by watching Acquisitions Incorporated, I'm mostly used to giant fights that happen months apart, and so I've now started to understand (after only what, five years of DMing?) that you can increase the challenge by simply stringing fights together without any obvious time to rest. Players will burn through resources early on and be running on fumes later.

I actually have no idea how the boss fight will go, which will be where we pick up on our next game this Saturday (my games alternate Saturdays and Mondays each weekend to allow people with tough schedules to play) after a cliffhanger ending this time. I think some players have been very conservative, holding some big fireworks in reserve, while others are pretty spent.

There's also the chance that the boss, who doesn't have a huge amount of HP, might go down relatively quickly (though there are some environmental challenges that will give him a buffer.)

Naturally, I want the party to succeed, but I also feel it would be appropriate to force the Grave Cleric to burn a Revivify given how climactic this fight's supposed to be.

We'll see.