When is paint too old? How long can someone keep a can of paint before it goes bad? Is storing paint for 10 years too long?
Most paint manufacturers say that the shelf life of unopened paint is about three years, so ten years is quite a stretch. To find out for sure, it is highly recommended that you perform the stir-stick test. Mix the paint thoroughly for five minutes, then dip a paint stir stick into the can, lift it out, and watch how the paint flows off.
If it flows evenly and looks clumpy or watery or smells bad, get rid of it. If it smells bad, the odor won't go away after you spread it on the walls. But even if the paint looks and smells alright, we suggest brushing it on the same material you plan to coat, to make sure it dries okay.
The best way to keep paint fresh, is to minimize contact with air by sealing the can tightly after each use and transferring the paint to a smaller container when the can is half empty. And you'll thank yourself later if you label and date it.