AP refund - any time limit to request

Is there a time limit to when you can request a refund on an AP?

Wife expires in 9/3. Vacay plan for 8/23-29. We might consider scrapping the whole trip but do we need to decide (e.g. request from wdw) on refund versus extension BEFORE the parks open?

For example, all parks open on 7/15, can I on 8/1 decide for a refund or is it too late?

I have no idea about if there is a time limit on refund, but I remember there being a time limit on the renewal discount.