I just want to start by saying I'm very relaxed about this - I'm getting enough sleep, DS is getting enough sleep, I'm easy.
Basically, most nights since he was born, I have been letting him fall asleep whenever he was tired, and taking him up to bed when I went up (whether he was asleep or awake as by that point, as he'd usually go to sleep when we were cuddled up/he was feeding/it got dark, if I just put him in the bedside cot).
I don't have a problem with doing this, except for that it is quite nice, if I do put him up to bed earlier, to have the undisturbed time in the evenings. I look after DS all day and DP doesn't help even when he gets home so it is nice to have a break.
However, when I do this, he half wakes up about once every 1-2 hours, I feed him and he goes back to sleep. I don't honestly know if he wakes during the night for milk as we co-sleep and I either move him closer while half asleep myself or he helps himself. Should he not be able to sleep for longer than this by now? He does have naps sometimes which are 3 or 4 hours. And at 5 weeks old, he was sleeping 7 hours!