I just put the second replacement pivot bar on my MTD-branded MTD 46" 21hp B&S rider that I bought for about $1100 in 2004. It has a variable speed pulley-type transmission. I've had to replace all the belts, with the deck belt being changed at least four times. I replaced the plastic drive gear on the starter a couple years ago. I bent the first pivot bar the second year I had it, I think, because this particular model has a really tight turning circle that they got by hanging the wheels in a weak configuration. You can turn the wheels almost 90 degrees, and I can easily go around a 5' fence circle, which I have a lot of to keep the deer off my trees. I popped the front left wheel off at least twice, by hitting ruts while going fast and trying to turn tight, and it was that force that bent the pivot bars. This time I went with the cast iron pivot bar and I'm hoping for a couple more years out of it before it dies.
I change the oil every year and the air filter when I think of it, which has only been once so far. It gets used really hard on some very rough ground, and this year especially, I've been cutting tall wet grass.
I must have ended up using a higher quality cotter pin to hold the wheels on since I haven't popped one of those in a couple years now. I spent $150 for the cast iron pivot bar plus thrust nuts, and some plastic bushings I didn't need with the cast iron bar instead of the pressed steel version. The bar itself was $116. I can find any part at the MTD parts site and they get it to me in about a week instead of the 10-14 business days they say it will take.
It may be a POS, but it still cuts the grass even, and it only chugs on the really tall wet stuff where just about any mower would. This is the 7th cutting season. The deck is still fine and the spindles just keep turning. The variable speed pulley system is amazingly simple, and apparently sturdy. I can go way faster on the thing than my back can take.
Because what I cut is so odd shaped I really don't know the area, but it takes me at least four hours to mow, and five if I mow parts I don't hit every time. I can get most of that done using a little over one tank, which I think is maybe 2.5 gallons. I'm usually moving as fast as I can stand.
Chuck