I agree with the Maintenance points that have been made. There are guys that can tear up an anvil with a rubber hammer. ATVs don't last long for them. My wife has a 05 Yamaha Kodiak with 4300 miles on it. We just had to have the engine rebuilt but not because of a lack of maintenance or abuse. The air filter in the Yamaha's just drops into the air box. You have to grease the rubber seal to keep air from getting between the filter and the intake. Well it's a very poor system and we ride in a lot of dust most of the time and dust gets into the intake and eats up the rings and cylinder. I am working on coming up with a better system after dropping $1,000 in the engine, but that is still cheaper than $7,000+ for a new quad. My point is, anything can cause wear on a quad, mud being the biggest enemy. If you ride in a lot of mud, your up-keep will be higher for brakes, bearings and if water gets into the engine, well, that can be big. Take care of a quad, service it properly, ride it like you didn't steal it, and it should last many years.