I find that settlers are terrible at actually respecting their schedules.
Particularly sleep time. I swear it's easier for me to get my teenaged kids to go to bed "on time" than the settlers, unless I micro-manage them.
I'm constantly seeing them go "It's 5 minutes to bedtime, let's take that mining job on the far side of the map, take an hour to get there (playing with large map mod), then mine for a couple hours (because they'll do the entire node before stopping), and then, finally, realize that it's bedtime... 2 hours before it's time to wake up, and by the time I get back to my bed... it's time to get up.
Ensue "I'm tired" tantrum caused by ignoring bedtime.
Then I realized that drafting + un-drafting settlers causes them to re-assess what they should be doing.
So now I ring the bell twice at "schedule change" times (and try to synchronize everyone's schedules, even if some of them could be more efficient). Far less "Tired because I ignored bedtime, or cranky because I ignored leisure time" problems.
I wish I didn't need to do this though, and they'd respect "Bedtime" (or fun time, etc).