I look at it this way: if I can fit it in, on, or approximately near my existing safe without my wife complaining, I can buy it.
(I've got an 8-gun safe, which in marketing speak translation means it can hold 8 Davey Crickett .22s comfortably.) So, I'm pretty much full-up. I'm OK with limiting myself to "only" 8 long guns, provided it doesn't include the ones that have been handed down, or pistols. If you pick wisely, you can cover most of the "niches" with your favorite and not suffer too much:
* .22 plinker
* .22 target (w/ scope)
* HD shotgun
* bird shotgun
* long-range scoped rifle
* homeland security rifle (AR/AK)
* 1 or two milsurps
Substitute where necessary...
That's what I limit myself to. I do (basically) the same thing for pistols, though not so much (because they're less of a burden to lug around in a move, to the range, etc. and are much easier to shoot 3+ at the range per trip.) I don't like selling things - more hastle than it's worth, and usually doesn't return what you've put into it - so I typically don't. I'm at 5 long guns right now, and I don't feel I'm hurting.
Now, granted, I don't include "project guns", which are milsurps and/or cheaper guns I've gotten to repair or refinish in some fashion. There are only so many hours in a day, and so many days in a life, and unless you intend to truly collect firearms, it seems to be a waste of both time and money to keep buying them; I'd wager most "shooters" spend more time buying or preparing to buy a new gun than they do actually shooting. I don't see a point in that.
