Most of my experience is with production-level routers. What I see is that while the frame and components can still be sturdy, the MRO costs become more frequent and more expensive: Spindle replacement, limiter stops, etc. Also, the software just becomes obsolete. I view routers like edgebanders: You should plan no more than a 10-year life cycle and perhaps 2/3rds that if you run it hard. Though many folks limp their machines on for longer. Just my observations.

Erik