I never keep the zip files
I use each kit multiple times. I never used to but now I do, some I’ve used 3 or 4 times.
I never delete kits. Like never ever
If a designer retires I put (retired) next to their name so I know I can’t upload to the sad gallery anymore. If an active designer retires a kit I just leave it in their folder because I can still upload any pages to the gallery.