Other grasses, depending on the variety, typically last up to three years in storage. Germination chances are still reduced within the storage period. For example, you need more seed to cover an area, compared to fresh seed, because a certain percentage will fail to sprout over time.
I've kept some rare prairie grass seed for over 10 years in a ziplock – in a freezer.. kept in a controlled humidity, cool environment they will be viable a lot long.
Grass seed, like any other plant seed, has a finite shelf life. Grass seed stored for more than one year gradually has fewer seeds that would sprout, or germinate, .