Question about powder formula

My son is 7.5 months and last month we started him on powder formula since he was getting older. He’s been drinking the ready made since he’s been born so this is new to me...

When you buy the water jugs do you refrigerate the water after opening? How many of you leave the water out so it’s room temperature? How long is a bottle good for?

My son hates cold bottles.. & to be honest I’m over heating the bottle up since he really doesn’t need it to be warmed up anymore. Haha

Give me your feedback please! 😊