Pretty much, yes — how difficult this is depends on how the child is dressed, of course. Once he is in trousers and t-shirts it's a fairly trivial exercise. You don't have to be constantly doing it, though — every couple of hours is probably enough unless there are other clues or he is drinking a lot. You can sometimes go by smell, and there will inevitably be the occasional damp-trousers incident (it happens with disposables too).