XMark 52", it has probably cut in excess of 10000 yards...almost ten years old...mechanically, one spindle blew up bearings, was fairly easy to change, the bearing went at about seven years, with that exception and with normal/routine maintainance it will probably outlast you !! Keep the blades sharp and change em at least once a year (more often if you're doing the commercial thing) keep the oil and filters clean...
Highly recommend the XMark commercial series !