Let's talk lawn tractors for a moment. I have a John Deere D140. This is a box store model that I purchased from a John Deere dealer. There is a 100 series (box store,), a 200/300 series (advanced homeowner,), a seldom seen 500 series and then the 700 series available with a water cooled three cylinder diesel. The lower end consumer models have decks with sealed bearings. The higher end models have serviceable bearings, better decks, beefier frames, better engines, etc.
My D140 is now in season ten with 285 hours on the clock. I've been averaging 30 hours per year mowing 3/4 acre of sloped lawn. Thirty years at this rate would come to 900 hours and I have faith in basic B&S V-Twin to easily survive that with regular maintenance. I have far less faith in the deck and spindles. That being said, my up front cost of $1899 comes down to $190 per month and that figure is likely to fall as the years go on. The weakest spot in these box store lawn tractors is the hydrostatic transmission.
If money were no object I would have a lawn tractor with a water cooled engine, preferably diesel, a beefier deck, better transaxle and serviceable spindles on the deck. I believe that such units start north of $12k. I would be happy to break one in and write a review for anyone who has the coin.