I wouldn't worry about "normal" - as you can see, everyone's kids are so different. My DS does 2 day naps - one for 40mins, and the other for 1.5 - 2 hours. He will then sleep 8:30pm(ish) - 6:30am(ish).

I would LOVE DS to do a 4 hour day nap - you must get so much done! Enjoy it