My son, who is now almost 5, would never nap in a stroller. In fact, he only fell asleep in a stroller once that I can recall before we went to Disney this past spring. He napped every day. My daughter, now 16 months (10 when we went) would fall asleep easily. It really depends on the child. From my experience, once they get more interested in their surroundings, they will want to see everything and will sometimes fight sleep. Once they get mobile, they will wear themselves out and basically just pass out in the stroller or car seat. It's amazing how they can go, go, go, then fall asleep in a matter of a minute or two.