That's a comparable rating to the NMC Lithium cells used in an electric car, yet an EV can typically get > 200,000 miles from their cells. A charge cycle is defined as 0% -> 100% -> 0%. If you never do that, you get a lot more effective charge cycles.
Edit:
That's not the full explanation. 300 miles of range for a typical EV * 1000 cycle rating gives 300,000 mile rating.
You likely charge a lot more than 1000 times over those 300,000 miles, but a partial charge counts as a partial cycle.
It should be said that at that point you don’t have very many charge cycles left after the capacity drops below 80%, and the capacity will drop a lot faster for every charge cycle after that point.
I don’t have exact numbers.. based on graphs I’ve seen I would guess that if the original cycle life was 1000 cycles you may have another 500 cycles until the battery is actually unusable. But it probably depends a lot on the specific chemistry and how the car is used.
Edit:
That's not the full explanation. 300 miles of range for a typical EV * 1000 cycle rating gives 300,000 mile rating.
You likely charge a lot more than 1000 times over those 300,000 miles, but a partial charge counts as a partial cycle.