Heck, our stick house was built in 1911 so I expect the 5er to go that long.....;).
Seriously other than what has been said, to me it can also come down to technology in the newer rigs than the older. Ours is an 05, tank gauges aren't too accurate, no propane tanks that slide out, no 6 point levelors, etc. we've updated some things like a flat panel TV, but for the most part aren't too concerned on the trinkets. We purchased it used, looked first at the floor plan we wanted, then condition till we found the right one.