Store 0 nic PG and VG in a cool place, at least normal room temperature cool.
With nic, the main culprit is oxygen. Next is heat and light. For long term storage, keep it in the freezer.
I keep large, unopened bottles in the freezer. Opened large bottles are broken down into smaller ones and stored in the freezer. I keep the stuff I use monthly in the refrigerator in a smaller bottle.
Try to minimize air space. If you have large bottles, get small ones, preferably cobalt blue or amber. Break down the large bottles into the smaller ones to minimize the amount of air that's in contact with the
juice during storage. Fill them very close to the top before freezing. Unlike water, VG and PG hardly expand at all when they're frozen.