Past the age of around 15 to 18 months, I really don't like to give a morning nap time. In fact, I tend to try to avoid it after 12 months and move to a longer afternoon nap if possible. That said, sometimes it still seems necessary. So I will keep a morning nap to about 45 min (less than an hour, for sure) and make sure the little person is asleep early enough to be awake by 10:30 or so, which means there is still an hour and a half before lunch, which is immediately followed by naptime.