I think of "too many" in 2 ways
- clearing clutter
- buying new ones
So for me "too many" means:
- Closet is so packed things are falling off shelves. Closet review time. Uh oh, I have at least one bag I haven't worn for a looooong time. Did I like it before but I grew out of it? Did I buy it because I loved the way it looked but it's totally impractical for my life? When will I realistically wear each of my bags next? I try to make an honest assessment of the situation including any mistakes I've made.
- That new bag is cute!!! But I already have a beautiful bag (or more than one) for exactly that purpose I'd use that new one for, meanwhile I don't have one for some other purpose. PASS. (Or, maybe my bag collection is fine but I have no good winter coat now, etc.) Many of us, and definitely me included, tend to collect a lot of our favorite types of thing and not enough of the other types of things we need.
I know this is not a hard number but I really think it depends on how many roles in your life you play and how frequently you'd honestly switch your bags. You really mostly start to realize you may have too much when you have that guilty sensation that there are bags in your closet that are not seeing the light of day, or you're making too much of a cut in your overall budget for bags and you know something else important is getting short shrift.