I have about two thirds of a 5 gallon bucket of my family room paint left from when we painted it 6 years ago. The first question is does paint go bad? And the other question is is there a way to change the sheen? It is a flat wall paint (kinda scrub green). I wanted to know if I could add something to make it an eggshell sheen so it is still almost flat but easier to clean and with a little sheen to it. Could I possibly get say a quart of the same type/color paint in a higher sheen and mix them together?