Diana and LisaP make good points - if you stop buying entirely, you can end up with a situation where everything is seriously dated, or, as has happened to me before, nearly everything falls apart right around the same time (always seems to happen with shoes for some reason, and jeans). Both situations can strain your budget because few of us can go out and buy a complete new wardrobe all in one fell swoop, not to mention the time that takes.
I've been thinking about this, what with trying to buy seasonally and plan ahead. I think it was Mo who posted a link to the Yogastic Shopping Planner who blogs about planning her purchases for the next four years. I thought that was the most peachy keen idea and sat down and wrote out a draft version of it for myself. I haven't followed it 100% yet but it did make me aware of how I should be more deliberate about replacing basics as I go along rather than spending all my $$ on fun stuff and then being stretched for time and/or money when all my gear sneakers, say, are three years old and should be replaced.
Of course, that approach requires identifying what your basics are, and keeping that list up to date as your lifestyle, body, and aesthetic preferences shift.
A 2 out, 1 in plan might work (or whatever ratio makes sense, 3:1, 3:2, etc.). Another option is to resell some of the 'nice but not me anymore' pieces, via ebay, consignment, Twice, whatever, and get a little money back - reduces wardrobe volume and guilt about 'wasting' perfectly good items.