I can't imagine that there would be a problem.
We use bottled water, and most of the time don't put it into the fridge.
As long as the bottles are sealed to keep out dust and things, you shoudl be just fine!
It's amazing the tips you receive from people sometimes, that you say "WOW, Can't believe I never thought of that!!!". The tip about the bottles you're describing was one of those lightbulb moments for me too!!
I always struggled on how to keep his formula cool while we were out and about - we always carried a cooler with ice packs! :shock: One mommy I knew finally mentioned doing it the way you were told, and I went DUH!! What a great idea!