Armor is for wimps! Warrior Mages RULE!
Seriously... My readings of real soldiers in real combat conditions throughout the ages leads me to conclude that tough guys can withstand conditions that are simply unimaginable for everyone else. And since I want to think of adventurers as TOUGH guys [using the modern gender neutral meaning of 'guys'], adventurers would just sleep in their armor as best they could - comfort be blasted.
Mind you, if they've put themselves up in an inn and/or have no reason to believe danger is lurking, they are going take the armor off. So, unless the characters have GOOD reason to believe danger lurks, it should be assumed they take the armor off. Just like you don't leave horses saddled up or bows always strung. You can - but over time bad things would happen.
In game terms, if the players insist on never taking off their armor, they should get infections, rashes, mental illness from lack of sleep, etc. So you could start imposing general penalties for all actions due to poor cognition and poor health. You could impose the penalties after 2 - 6 days of continuous wear. That way, they could be TOUGH guys in the short term, but too many days in a row would wear them down which is pretty realistic actually.
As far as donning armor in an emergency situation, I think characters are probably going to don whatever armor they can in the time alloted. Helms? Two rounds. Simple breastplate? Probably manage it in 6-10 rounds. Mail shirt? 3-6 rounds. Studded leather? 3 - 4 rounds but not laced up. But greaves, vanbraces, weapons belt, fancy heavy plate mail? Forget it. It'll take minutes and the fight will be long over.
Robin