Here's the thing: most new books that get hyped and sell well have short-term success. I don't mean that they're bad books, nor do I mean that they aren't successful. Most, though, just aren't worthy of particular mention a few years down the line. By stocking up on current hits, I'm not allowing time to tell me just how "eternal" and "classic" these books really are.
I have always managed to keep my stacks under triple digits, but of late I've been straying dangerously close (and am way over if eBooks count... which they don't!). I didn't buy all of the books for no reason - continuously hoarding will only mean that at some point I'll entirely forsake books that I truly wanted to read. So now I visit books that have long been on the shelves - I'm currently reading The Day Lasts More Than a Hundred Years by Chingiz Aitmatov and am finding that it's actually rather good (and not at all what I expected). I finally got around to reading Solzhenitsyn and completing anything by Thomas Mann. I'm making headway in the stacks (with a few library stops along the way) and the conclusion is simple: while new books may be flashy, I have plenty at home to keep me busy for a while. No reason to go book buying within the next two years.
Okay. Maybe more like two months. But for now, I'm doing okay.