Do these before they expire
Act 3 is a city of quests. The clocks below are the ones that fail quietly if you clear the "boss" first or rest too often. Everything else can wait for the Morphic Pool warning.
If Gortash is defeated before you travel to the Iron Throne, the prison is destroyed and Duke Ravengard dies there. If Wyll still has Mizora's pact, she can bring the Duke back at camp afterward. The wiki treats that return as the pact outcome, not as the prison staying open.
Going to the Iron Throne ends Gortash's offered alliance. He and Wyrm's Rock Fortress become hostile when you approach afterward. Disabling the Steel Watch at the foundry is the other way the notes describe making the fortress fight easier. Attending the coronation is still available before either of those breaks.
Counsellor Florrick is executed after the fifth long rest once you have read the execution notices in the Lower City, or once Duke Ravengard tells you about the execution at Gortash's coronation.
Before the Lower City, and before the end
Entering the Lower City before you meet Jaheira's contact at Danthelon's Dancing Axe overruns that hideout. She still asks for help finding Minsc, via a messenger rat at camp.
Help the Devilish Ox ends when you enter the Lower City if you met the Strange Ox in Rivington and have not finished with him.
The Morphic Pool is the last popup on the time-sensitive list. Patch 5 also blocks joining an active multiplayer game once the party has reached the Morphic Pool or gone past it.
The city clocks that are rests
Florrick's execution is counted in long rests. The camp page is the supply cost behind those nights.
Official site: baldursgate3.game.