You are right - if it works, why change it!

If your LO is not waking in the night, I wouldn't worry too much. It is good that he does not fall asleep, just relaxes with the bottle. My LO had a bottle as part of her wind down routine. I wanted to get rid of the bottle at 12 months. To phase it out this is what I did:
Our nap routine was - diaper change, bottle and music then nap. I changed the routine to bottle and music, diaper change then nap for a few days. Then I did bottle and music, diaper change, book and nap. Then I started to offer milk in a sippy during the book. So our routine turned into – diaper change, book and sippy of milk, then nap.
Our bedtime routine was – bath, music, diaper change and jammies, bottle and bed. I changed to bath, music, diaper change and jammies, bottle, then book and bed, Eventually I offered the sippy instead of the bottle. I waited until we first weaned the nap bottle.
I hope this helps! Like I said, I don’t think you have caused a big problem. He sleeps straight through, so that’s great!

Christine