1. Do you also save the zipped files?
Nope!
2. Do you typically use each kit to make just one page, or multiple uses?
Depends on the kit, but most of them multiple times
3. Do you remove kits from your 'database' once they've been used as many times as preferred?
I don't remove kits if it still fits my style. I don't have a "preferred" use limit. HOWEVER, if I know it doesn't fit my style, or I won't ever scrap with it again, then I will delete. I'm all about the purge!!!
4. How do you handle kits that are retired/from retired designers?
Retired designers go into a misc. designer folder since I can't use them for challenges.