You may have considered storing grass over the winter or for an extended period of time. However, keep in mind that grass seed does expire. The bags that hold the grass seed commonly feature a stamped expiration date that you should reference when you initial buy your grass seed. Of course, avoid buying expired seed.
Grass seed is typically expense, which may inspire you to try to use the seed anyway despite the expiration date. If you use expired seed, be aware that you may not have desirable results. As the seed moves beyond the expiration date, the number of seeds that will germinate diminish over time.
We would try to grow grass seed that has been properly stored for up to 3 years. When using dated grass seed, you should consider the costs involved in trying to grow the seed. Things like water usage, starter fertilizer, and soil can add up quickly. You may not want to risk seeding a large area with old seed due to these costs. However, if you have a small 50 square foot area to refurbish, as an example, give seeding a try.
The key is to use your best judgment when using expired seed. Weigh the costs, labor time, and the potential hassle of reseeding the area again if the seed fails or grows in thin. It is hard enough to grow fresh seed. In many cases, it may be best to just buy new grass seed if you have any doubts about its potential to grow. Good luck!