I go a long time between changes, using synthetic. I always hang on to the extra 1/2 quart for when/if the sump needs some topping off over time.
 

My old truck (R.I.P.) took 14 quarts. It came in gallon jugs so each change took 3 1/2 jugs. So half of the time I had a half full jug sitting on the shelf and never had any issues with oil. The truck had 285K miles on it and was still going strong when I loaned it to a friend and she wrecked it.