I have about 2,000 CDs, which is a lot by the standards of the world at large but small potatoes by the standards of THIS forum!
I tend to buy in batches or spurts as well, typically from online vendors like The End or Laser's Edge, sometimes from DeepDiscountCD since they have free shipping. I'm a mean ol' bargain-hunter.
Recently I picked up a fair number at MediaPlay, since they've gone under and CDs were 80% off. And of course, record shows (hi there, Ned *boom*) and godHelpUsAll, at ProgPower.
I'm also a deejay at a radio station (WREK-FM) and sometimes score promo CDs, or I'll burn a copy for later. I buy the CDs I really like, though; I've got witnesses.
For a typical month (i.e., not September), I used to buy an average of 4-8 CDs. That flow has slowed to a virtual trickle after buying a house; after I pay off my car, I can resume my consumerish ways.