Funnily enough I was having a convo with a friend about making formula up and she highlighted how different guidelines are across the world.
From memory, here the latest advice is.
Boil fresh water (not reboiled water as the mineral contents become concentrated with each boil).
Within half an hour of it being boiled pour the water into sterilised bottles and add the powdered formula. this ensures the bugs have been killed in the water (by boiling it) and the formula (the powder isn't sterile, but putting the powder into boiled water does kill bugs).
Rapid chill by placing under a cool running tap.
Make each feed as and when needed.
Whilst I can see that this method (fresh feed for every feed) is tricky in practice, I do understand why they are the guidelines. The government/WHO give us the information to prepare the milk in the very best way possible (ie reduce risk of illness). However if 'we' choose not to prepare that way we are doing under our own steam. We have been told what the optimum ways are to prepare milk and we either choose to follow it or not.
In some EU countries they use the above guidelines for preparing the formula, but say you can make 24 hours worth of feeds and keep them in the fridge, as long as you put them in the fridge as soon as the rapid chill has been completed.
I think different babies like their milk at different temperatures, so I guess wrt that it's a personal thing for that particular baby.
I know around about this age a lot of ff babies go off their milk. One theory is they're bored of drinking the same thing all of the time, as unlike bm it doesn't change flavour. Then subsequently they are weaned early because they aren't drinking as much milk as they previously were.
I lol'd at the magical powers of Evian too! It's so good it makes your baby roller-skate dontcha know 
Lis, I keep meaning to put a picture of ds on my profile. Maybe we should start a FB group?