Well, at 11 weeks old, he should be able to go longer than 2.5-3 hours at night. BUT, he should also be having about 2 or 3 naps (2 naps being about 1.5-2 hours in lenght) I think...but I could be wrong. I wouldn't let him sleep longer than, say, 2 hours at a time during the day if you worry about robbing his night sleep. Are you dreamfeeding or clusterfeeding? That might help with the frequent wakings. Does he take a paci? Perhaps you could offer the paci instead of feeding him when he wakes at night....just some thoughts.