Emma, I demand fed our boy on advice from our paediatrician and it worked well for us. I think it is something you have to keep an eye on because you can overfeed on formula. We never had that problem and he is still in good proportion with both his weight and height in the 99th and 98th percentile. I guess you can just keep a close eye on weight gain vs height? Feeding our boy when he wanted it and until his was full really helped us on the sleeping front. Over time he regulated his own feeds and now only has a bottle every four hours and has tapered back on the amount he drinks now that he is on solids. I will definitely demand feed our next bub.