An unopened paint can can be stored without deterioration for several years. After it's been opened, it can be kept in a warm, dry place with the lid tightly closed. Water-based paints do not withstand freezing, so don't leave your paint in the shed over winter. Tip: If you think you may not use all the paint at once, don't dip your painting equipment in the can as you paint. Instead, pour the paint into a separate container, such as a roller tray - this way you won’t transfer contaminants to the can and the paint will stay usable for longer. Clean the can's edges and lid and close it tightly for the next use. Be sure to mix the paint thoroughly before the next paint job.