68 barracuda top rear window question

Wont be to that point for a few yrs on my 68 Bcuda..... but the rear glass in my 69 Fury has never been unzipped and goes up and down with the top just fine for 12 years now. "They" recomemd unzipping it for lowering/raising, and it is a good idea... ive just been to lazy to walk the aft deck in the barge to reach it. It is up and down many, many times a year.