On average I'd say they nap 2x/day up to 18 months, but I've had quiet a few that need it longer than that. You know it's time to go down to 1/day when they really have difficulty sleeping in the afternoon. The longer they do 2/day the better, imo! I would try to make sure that they do nap at the same time, however, or else your whole morning will be tied down by naps. Usually dcks are up relatively early, so I try to do am naps early....and they're not usually too long, unless they're super-young.