When do you stop waking them up?

I was told when my daughter was born that I need to wake her up every 2.5 to 3 hours to feed her and I was just wondering when I can stop doing that? I quit doing it at night because she sleeps for 5-7 hours at a time but I've been sticking to it during the days for the most part. She's napping right now and it's been a little over 3 hours since she last ate and I just don't know if I should wake her up or if she's fine. She's 4 weeks old and she gained back all of the weight she lost at birth plus a pound.