I tend to time the move from playpen to cot to coincide with the move from crib to bed at home. then you have the parents generally also reinforcing the stay in bed like a big girl/boy or it is back to the crib like a baby concept.

My kids in playpens are in family bedrooms but those on mats are on my mainfloor (diningroom) so not totally out of earshot and I can peek in on the frequently.