My only just 3 year old has always had a good 2 hour nap, 1-3pm, and then bed from 8.30pm and slept til 7am ish, The last few weeks he's been really trying it on at nap time, even though he looks tired, and sleeps for at least an hour when I finally get him to calm down. Is this a sign that he's finished with naps or is it a developmental thing and should I persevere?