This thing has never let me down on its own. Batteries have failed, fuel has been bad, and belts have aged and flayed around, but it has always started, run, and mowed like mad.
We bought it used for around $4K circa 1992 with less than 200 hours on it. It's been run about an hour every ten days or so since in the mowing season, and with the rare Cat 0 hitch, has 30 or so hours of snow removal on it as well. Keep the fuel clean, battery fresh, filters and oil changed, and these things will run forever.
It seems to be rough on air filters because of the location of the intake hose, but other than that it's been a champ. Only major glitch was the ignition switch failed on me. The mower deck is starting to show its age. The deck itself is wearing and rusting through. The mechanicals are just as stout as ever