Interior latex paint can last for many years if it has been stored under proper conditions, according to DecorColor.com. It will remain usable as long as the metal can has been properly sealed, kept dry, and stored in moderate temperatures.
Paint cans should be stored in a dry area that is kept between 32 and 90 degrees Fahrenheit. Transferring the good paint to newer containers for longer storage helps to preserve the paint, since the metal can is prone to rust. Additionally, if the lid has been repeatedly removed, it is possible that the protective seal of the liner can become damaged, allowing water vapor to get in and ruin the paint.