a few years ago i found a case of paint that had been stuffed under my bed for around 8 months, it was kept at a normal room temp for this time and ever single ball shot perfectly!
if you are storing in pots i would not advise leaving the lid shut for a couple of reasons, first the pressure on a packed pot will cause flat spots on the paint and also any mosture trapped in the pot cannot escape.
in short, keep it in the box if you can and normal room temp is fine.......if storing for a long time turn the box over (ie stand it on the lid) every few days to stop it flat spotting.
leaveing paint in the car over night before using it is a VERY bad idea.......you may as well not bother as you will be cleaning your barrel every other shot