The length of time in which you can use a pool cover will depend on its quality. Quality, in this case, is in terms of the material and structure of the pool cover. The best materials make durable pool covers. As long as the pool cover is also well constructed, you can be sure that it will last you a while.
You should also keep in mind that if a cover is used frequently, it is likely to wear out faster than one that is taken out occasionally. Lastly, remember to handle your pool cover with care so that you can use it longer.