My teammate has a CAAD8 that he started racing on 5? years ago. With only minor changes it's still his only road bike. Changes include fit, wear parts, wheels, and a shifter upgrade. He has no immediate plans for selling it.
I'll race a frame until I get something better (and I'll buy a frame for a variety of reasons). I don't see myself changing frames for a while now since I have two custom geometry frames with the same setup.