Easy - I never have more than 3 or 4 kits in the stash at any one time . Anything more than that and I start to feel overwhelmed.
Don't really care about collectibilty or rarity, I just build what I enjoy (planes and the occassional tank). The only "must have" I have on the horizon, is that new 1/32 B-25 that's coming out in a few months. But, it fits right in with what I normally build, so I don't mind that it may be considered a "specialty item", because of it's limited production run.
-Fred