I'd be ecstatic if I got 20K miles from rear tires. In general, I go through 1 set of fronts for every 2 rears. I think I get 12-15K miles out of the rears. I'd have to check my maintenance spreadsheet to be sure though.
This reminds me that I need to do something about "winter" tires for the STI. Thinking about going all-seasons year round on that car, but hate the thought of neutering the summer performance - but that's why I have the M3, right? I need more money.
Anyone rocking all-seasons year round?