I guess my question is- should I wake him if he sleeps more than 3 hours in the daytime?
I did. Reason being that I was told by the midwives that babies will usually have one longer block of sleep in a 24 hour period and if you let them sleep for 4+ hours during the day then you might be up all night with them
As it turned out with my younger two, I had to co-ordinate their routines around school and kinder so they never had the chance to sleep that long during the day anyway and they were my best two over night sleepers. DD slept through the night at 5 weeks