at almost 4 naping 1.5hours, I'm kind of thinking that you have the answer. My 3y 4mo won't be asleep before 9pm & up at 5.30am if he naps for more than 45mins, if he naps for 30-40mins I can get him to bed by 8pm & up at 6/6.30, but if he goes to the hour mark we get about 9.5hours night sleep. Most of the children who we are friends with have given up naps because their night sleep suffered too much.