The market has changed quite a bit the last couple of years. 10 years ago, I would wait for certain titles to come up for sale, and buy the titles I thought I really wanted. Rewind to about 5 years ago, and the market started to dry up (and is pretty dry now), so I just started buying anything that was a decent deal. For myself this is the best way to go for a couple of reasons- I get to play games I normally wouldn't have considered, I don't lose my butt on them when I go to sell, and it gives me trade-bait for a machine I have more interest in down the road. trading has picked up in popularity quite a bit, and is even easier to do when you aren't attached to a particular game.
Ironically, I just picked up a Funhouse and Buck Rogers for $1900 (Plus 200 in gas and tolls), with no interest in either (have already had Funhouse and thought it was just okay), but knowing down the road I can parlay those into something I have more interest in.
My longest wait for a title I wanted was 3 years (CO1812), and it was ROUGH. But the price was right and it was a project that pushed my skills to the limit. The time you wait for a machine is directly related to how much you are willing to spend