Thought I had answered this some time back, but it must not have posted. I'm no chemist, but we do have one on ECF, and he says that both pg and vg are antimicrobial Do not need to be stored in freezer or even the fridge. I probably wouldn't put em in a burnin hot garage, but keep em room temp, and maybe outta the sun, in a closet or sumpthin. They should be fine for a year or so at least. Quite possibly longer