As my 21month old seems more often than not have a nap when he is at our CM's, resulting in constant screaming when he gets home or crashing out asleep at 4.30 when he gets picked up. Also then on my days off he has mammouth 3/4 hrs naps to compensate, which is excellent for my MN/housework time but not so good when I want to make the most of the time I have to spend with him.
BTW I do appreciate that when busy/doing activities/ out and about it is not always possible but it seems more often than not that he goes without a sleep.