If I could afford to, I'd probably buy a new one each or at least every other year... Just to keep it "new". New toys are always fun.
I have an '04 Vipertec. I picked it up at the end of the '04 season. I really like it and can shoot pretty good with it.
I get tempted at the proshop when I see the new Switchbacks & Trykons... But I have to draw the line somewhere since I have a family to support now.