I woke them during the day after 3-4 hrs in the first few weeks, never at night (though waking wasn't a problem!) I woke them in the day in the hopes of getting the day/night sorted, especially for DD who was awake nearly all night for the first few weeks and wanted to sleep long periods in the day. Both breastfed.
I think if they are over about 3kg/7lb you probably don't need to wake them (definitely not at night), unless they are jaundiced or something.