I think I've slept in my clothes most of my life, if not definitely middle school and on...
I can't remember the last time I actually slept in pajamas, though there's been a time or two I've sleep in boxers (w/ briefs under)...
I also have had bad sleeping schedules my whole my life though, don't sleep normally at all...
I can sleep on chairs, beds, couches, carpet, tile, floor, etc...