From 6 months I started dropping the feeds. Are you b/f or f/f? The reason I ask is if you're b/f, then you could try reducing the time you feed by, every 3-5 days. If you're f/f, then try reducing the amount you give him in the bottle, anywhere between 10-50ml every 3-5 days. And see how that goes. You could also try offering water instead of a feed at night. This could take up to 5 nights to work.
HTH.