I have severe insomnia and I can be up for weeks with very little sleep it sucks. But with everyone in my flat asleep I can be little for a while and even though I still can't sleep being little distracts from it.
I'm usually a sound sleeper but sometimes I'll wake up in the middle of the night and "add" to the wetness of my diaper. It is a nice feeling, and even if I have trouble going back to sleep, I really don't mind because I'm in my "little space".
Anytime after like 12am to a few min after I get up I'm in little mode. Also if I wake up in morning like an hour or two before I have to get up I'll grab my paci and fall back to sleep(I don't use paci all the time because it makes my teeth hurt.) I normally fall asleep at around 4:30am.