It’s difficult to say how long your cover will last, because it depends on the unique conditions that any cover faces. Occasionally inspect your cover to look for signs that it’s not working properly. Does it look like it’s in contact with the edge of the hot tub surface all the way around? Are there any tears in the outer cover?
Cleaning and treating your spa cover, maintaining proper water chemistry and gently removing leaves, snow and ice will help your cover last longer.
You can find out more details on hot tub cover care from this article.