A reader has a method he says greatly increases the lifespan of a can of paint.
“Long ago I learned a technique to make paint last almost indefinitely–in quantities of 1 gallon of less (though it might be possible with current plastic 5-gallon buckets). Making very sure that the cans are tightly sealed, turn them over every year or two. Today I’m painting with a long since discontinued Flecto plasticized Varathane enamel. I first opened and used it 11 years ago, but had always flipped it every year or two. It does take about 3-4 days to dry, but I’m betting it was slow even back in the day. This is the third “opening,” and it’s behaved the same each time.”