If your paint can lid is on tight, the outside of the metal can is kept dry, the can is full and the can is stored between freezing and 90 degrees the paint will probably last for many years. Probably what will go wrong first with latex paint is the can lining, that prevents the metal can from rusting internally will start to break down, allowing the can to rust from the inside. If a can of oil base paint is not fu II, you will probably find a skin over the top next time you open the lid. If the lid on a can of latex paint has been on and off multiple times, scratches in the protective can liner will allow water vapor to start rusting the can around the lid. If this is a concern, you may want to transfer good paint into another container for extended storage. Some latex paints I have found (none I sell, thank goodness) can spoil. The smell will tell you right away it needs to be disposed of Which lead s to...