Well, as you know you should always make up the feed fresh!
Having said that, in reality, there are times when you need it in advance.
The main thing to remember is this - the reason you are adding powder to hot boiled water is to kill the germs in the powder.
You would be amazed how many people think you boil the water to kill the germs in the water!!
I always make up the morning feed the night before....
Boil the kettle...leave about 5 minutes (you can leave up to 30, but no more or else the water is too cold to kill the germs)
Poor water into bottle.
Add your scoops.
Shake or roll!
Dump the bottle into iced cold water to cool it down fast.
Once it has cooled, whack into the fridge.
In the morning, reheat.
I'm pretty certain someone will come along to tell me I'm doing something wrong
but I did get this hint of mumsnet in the first place.
if you're still feeding in the night, make up a flask of hot water, this will save you waiting for the kettle to boil.
HTH