What's the best way to store oil paints long-term?

The main thing is controlling temperature, light, and air exposure. Keep your paints in a cool, dark place - ideally between 50-70°F - away from direct sunlight and heat sources. Basement storage works well if it stays dry; attics are terrible because they fluctuate wildly. Make sure the caps are sealed tightly after every use, and wipe the threads clean if any paint gets on them, since dried paint around the lid prevents an airtight seal. Tubes last longer than jars, but both need that seal.

Organize by color and keep a quick inventory so you know what you have without opening everything repeatedly. If you notice the paint separating with oil on top, just stir it back together - that's normal and doesn't mean it's gone bad. Tubes can last years if stored properly; I've used paints that were sitting around for a long time without issues. The real enemy is exposure to air and temperature swings, not time itself.

If you're storing opened tubes, consider wrapping the caps with plastic wrap before twisting the lid on for extra insurance against air getting in. Some people transfer small amounts to airtight containers, which works but adds another step. The simpler approach of just keeping everything sealed in a cool corner of a closet or cabinet does the job fine for most people.

Temperature and light matter, sure, but people forget that oil paints can actually separate or skin over if you store them tube-side-down for years - keep them horizontal or upright to stop that mess. Also watch out for those plastic storage boxes that off-gas in basements; the fumes can mess with the paint consistency, so if you're using a basement go for metal or glass containers with tight lids instead.

Are you storing tubes or already-opened cans? I'd push back a bit on the horizontal storage angle - keeping tubes upright in a cool, dark place works fine if the caps are sealed tight, and honestly most people don't have the drawer space to lay them all flat anyway. Where the earlier answers nailed it is the temperature stability; what they glossed over is that humidity matters just as much. I learned this the hard way when I kept supplies in my damp basement and watched a few tubes get crusty around the rim. A sealed container with some silica gel packets, stored in a cool closet or cabinet away from radiators, beats a drafty basement every time. The real enemy isn't the orientation - it's air getting in and moisture creeping around the seal.