The first thought that jumps into my mind is that if the leak is low, like toward the bottom of the liner, the liner will sit, dry, all winter, and likely will be destroyed by the first of next season. (Not to mention what it may do to the structure of your walls--I'll let someone with more experience with AG pools comment on that.) When a vinyl liner stays dry for extended periods of time, it loses its ability to stretch and when you refill the pool, will likely pull out of the track and not be able to be re-fastened. It may also dry out and crack...either way, you're looking at a new liner.

I think if it were my pool, I would drain enough water to get below where you think the problem may be in the skimmer, and just see if the leak stops. If so, you have your answer, and it probably can be dealt with next season. If it doesn't, you know it's below the return, and will need to deal with the leak before you close for the winter, otherwise you'll probably end up replacing the liner in the spring.

Janet