To be honest, I would be stoked if my 4.5 month old slept nearly 12 hours straight through, your son is a fantastic sleeper! I know the 5am wake ups aren't all that inspiring, but 11 hours is a long time for his little tummy without a top up, and it seems that is the magical time when his tummy gets hungry. I don't really have any advice other than to say that perhaps when he starts solids and they start filling him up he'll eventually end up sleeping in a little more? I'm not saying you should start solids either if you haven't, just maybe that it's something that will come about by itself when he's ready. Prob not what you wanted to hear sorry.