I try to stay 5-10 years behind. Seems the newer a car gets, the more the government has screwed it up(see comments about EGR for mini).
I run into the opposite issue--around 5-10 years old, the car screws itself up (stuff all worn out).
I dunno. Hate to pay the piper, but on occasion I too like to drive with the window down, and not smell every old vehicle on the road. Harder to diagnose a car by its sounds; but a whole lot easier to try to figure something out going by the trouble codes.
The current Prius's (Prii?) have proven themselves. I wouldn't have an issue buying one, and hoping to get 10 years out of it.