While I've never had a large number of guns (hovers around a dozen, and none are worth all that much), as someone else said, I only shot some of them regularly. So the rule is, if I haven't shot it in a coupla years, down the road it goes. I've sold a couple, working on a trade on another now, and will probably sell/trade one or 2 others. There are 1 or 2 that I want to get (and finances are a BIG problem) so the total number will remain similar.
There are a couple of exceptions: rarely shoot my HD shotgun (although I do shoot it a couple times a year.) and and unissued SKS, which while not worth a whole lot is the only "collector grade" gun I have, and remains unfired (by me, although someday soon I'll probably break down and shoot it).
My best shooting buddy does hoard somewhat, but he has alot of pretty valuable, rare and collectible guns(Dating back to the 1800's). And many are shot, quite a few of the not so rare ones, fairly regularly. he probably has nearly 100 guns (75% rifles, 25% pistols, only one or 2 shotguns.) so its difficult and expensive to shoot too many. Several he has to reload for (and does) as ammo no longer exists.