Sleep trouble

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My April '17 baby has a hard time falling asleep and I think he is simply not tired. He has a big boy bed so for nap i tell him he doesn't have to sleep, but he has to stay in bed. He always falls asleep for nap but I never let him sleep for more than an hour and a half. Bedtime is 8, last night he didn't fall asleep until 9. He wakes up between 6 and 7. How long are your April babies sleeping for nap and night?