My LO is 6.5wks now and he was born 7lb 14oz and now 11lb so putting on weight nicely and on 50th percentile. I've solely breastfed him and have fed him just when he wants it really...If he cries or is upset I just put him to the breast even if it's just 30mins/1hr since he last fed, he might feed again or just suckle for comfort. Or sometimes he might go 4hrs before he feeds again (I wouldn't have let him go this long before he was 3wks as I know they can get dehydrated and don't always wake even if hungry but was told after 3wks it was ok for them to go bit longer if they are putting on weight well which he is.)
So I'm pretty flexible with him and He seems happy with this but just wanted some reassurance this was ok or should I be trying to get him to feed at regular intervals like every 3hrs or just go with it?