Hi mumiloo, I fed to sleep with both DD1 & DD2. To answer your question, YES it worked for us.
With no long lasting issues.DD1 stopped at around 15 months when she was happy to have a cup of warm milk and a daddy cuddle instead. DD2 is just 1yrs so still feeding to sleep happily.

From 10 months I would be able to feed DD2 in the bedroom until she was relaxed then leave her and she would go off to sleep by herself. I also noticed that from this age she was able to roll onto her tummy & sleep much better.

I'm convinced she had undiagnosed reflux and the sleeping on her tummy has helped tremedously but that's another point.

i did introduce a sleeping bag from 4months as a sleep association tool and just now when i zipped DD2 into it for her morning sleep she giggled then rubbed her eyes and yawned. It works for us.

So if you're happy with it, keep at it i say. What a fantastic way to go to sleep - snug, warm, lowered heart rate (baby's) and cuddled.

I'd probably say the change in his naps etc is age related - such a lot of neurological changes going on at this 5 months onwards stage that it upsets the 'routine' for nearly every baby i know! It'll settle down again soon enough.