In my case, have 3 different finishes.
Mainly, I use 3 different colors with the same configuration. One kit is a little smaller (amount of drums) for one particular band.
Mine are (now) all the same make and wood, but I've already tried other stuff. What I have now is what I've liked, and kept coming back to.
Don't know if that would be considered hoarding, but it's nice to have the color options, and I have the space.
In your case, I'd say it's not hoarding at all, because your kits are different from each other.
On accumulating snares, if you are collecting something special/limited etc..., you're collecting for personal enjoyment, kind of like an art collection.
For "non-collectible" snares, it's cool to have a few different sound options available.
I think after 4 or 5, unless someone does a lot of different stuff, and records, it's not necessary to have a bunch of snares. I still wouldn't call it hoarding at 10 or 15 if someone really enjoys a good snare drum, even if something doesn't get played much.
At the least, IMO, anyone who plays out should have 2 snares--and bring both to gigs in case something fails. That's just being prepared and professional for your band, or whoever hired you IMO.