How about selling a piece of food or two.
The current 3,4,5 system to get full length of time is great, but lets say you know you don't need that much time.
Idea, if you have more food than you need for your next round, have a spot between each round to limit how much of it you will eat that round (say you only need half time, when full time is 5 food, you can consume only 3, save the rest, spoilage will still apply of course, but it will help you maybe have that extra you don't produce the following round if you will need more food that round.