I've never bought much, but I buy what I need/really want on a sort of drip-feed basis. Edit: much like Aizan, below.
Also, I only ever buy what I can afford. The idea of selling gear and taking a hit on it, or replacing it with gear that someone else has worn out, is bizarre as far as I am concerned. If it couldn't pay for itself, why did I buy it in the first place?
But that's a professional view, not amateur. I've been earning a good chunk of living from photography for so long that my views are skewed.
Cheers,
R.