i run a 15yr old JD 14sb and my helper runs a 9yr old JD 14sz. my kawasaki runs perfect, but the briggs is starting to burn a bit of oil, just enough to smell. just greasing the axle bushings extends life. the only problem is the wheels, they have a bearing and a bushing in them but the tread wears out sooner, wheels are $20 each.
i calculate my mower has around 1100 hrs on it. had to replace the rear axle and bushings because the previous owner forgot to grease them, but im still on the original blade clutch.