My daughter was on Colief for her colic (she is currently being weaned off of it) and we had no choice but to make up her bottles in advance. The Colief has to be put into the milk 30 minutes before she can drink it if we use 4 drops, or 4 hours before if we use two drops. With Phoebe feeding through the night we couldnt physically make the bottles up 30 minutes in advance because we didnt know when she would wake up and once she did if we made her wait 30 minutes she would be in a full blown rage by the time it was ready. Also through the day she never fed 'on time'. Sometimes she would go 3 hours between feeds, sometimes 2 or 4 so trying to judge when she might get hungry and make the bottle up 30 minutes in advance was a nightmare. I tried to follow the advice on the packet but with the colief I just couldnt and ended up in a bit of a mess. The HV told me to make 4 bottles up in advance and keep them in the fridge. She said not to keep them for anymore than 12 hours and we bought a thermos bag to keep them cold when out and about. Phoebe has had no ill effects from drinking milk that has been made up in advance. According to my HV the new advice to make up as you need the bottles was introduced because there were certain groups of women who were making a weeks worth of bottles up at once, or giving their child a bottle that had been left out on the windowsill all day. The milk companies introduced the new advice as it is a fool proof way of ensuring that no baby every gets an old bottle and therefore prevents them from getting sued!! Once Phoebe is off the Colief I will make up the bottles as I need them, but mostly because it will avoid wastage. If you need to make a bottle in advance and you are sensible about it you wont do her any harm xx