So I'm sure this is answered somewhere, but search isn't helping me. Basically - why do you want to shock the pool at closing? Is it to try and keep as much chlorine in the water as possible over the winter?
Reason I ask is we have an auto-cover, and we were told by the installer to NOT use the cover if we're shocking the pool as it could damage the fabric over time/shorten its life span. Sounds reasonable. He said if it's not safe to swim in, don't put the cover on the pool.