I think having too much is when your gear starts to stress you out. If you can't even remember everything you have or you feel bad about it, then that's your answer.
When they've nailed some criminal and publish a picture of his "cache of guns and ammunition" on the news and such, I just have to laugh!
I'm not a criminal and will probably never make the news for such, but they best have a gymnasium cleared to get mine laid out nice for the picture! And of my friends and family I'm only mid-grade...
You're at the point of too much, or enough, when it no longer makes you happy to add to what you have.