Exmarks are good quality machines. I worked at an Exmark dealership for a little while. They came in to the service department a lot less than the other brands we carried (Scag, Gravely, Husqvarna.)
You can still destroy a good mower, though, in 1200 hours. That's a lot on a zero turn. Has it been well maintenanced?
What engine does it have, Kohler or Kawasaki? Is it a Lazer Z?
Ben W. in VA