I'm assuming that the donning/doffing section in the PHB implies that PCs are supposed to remove their armor on a regular basis. It also makes middle-of-the-night random encounters a lot more serious if PCs are expected to sleep without armor. I skimmed the book and didn't find any obvious penalties for sleeping in armor (although it seems ridiculous to do so).
So are the PCs supposed to take off armor to rest/sleep? If they don't, should there be a consequence?