Back in 2005, when I was shopping for what will likely be my last new tractor, it seemed to me that the 4720 was a bit high on hp for that size. I opted for the lowest hp offered in the series (43 hp 4120). I also got the gear, "power-reverser" transmission and the base model 400X loader, but I did opt for the heavy duty bucket. That, and a block heater, added about $200 to the cost.
The tractor has held up very well for the last 16 years, needing only a new starter at about 5 years and new front tires at about 13 years. Only when I am Bush-hogging real heavy stuff, could I use more power. The tractor has the same lift capacity and hydraulic flow, as the 4720.
I also have about 1000 hours on it. The only maintenance it has had is engine oil and filter change every 100 hours, grease every 50 hours, and coolant change last year.
The Hydraulic oil and filter and fuel filter are original. I add Powerserve to the fuel in the winter, and Spectradyne conditioner the rest of the year. The tractor is not showing any signs of wear and has always been stored inside. I see no reason why it shouldn't last at least 70 years, just like the previous new tractor that was purchased on our family farm.
My dad is retired now, but he still uses that 1950 John Deere M, in his garden on occasion. I think part of the reason my 4120 has held up well, is that I have always taken it a little easy, knowing it had the least powerful engine offered in the series. Had i gone for the max back in 2005, I would probably also be running a "wreck" today.