From what I've been able to find, as long as you keep them at or below that 6kW, they seem to be good for close to 20k hours. Like any generator, the higher the load, the more heat produced, and the shorter the lifespan of the windings. It's why I've asked the question about making sure things are balanced. I have to build a splitter for the 240V plug, and make sure the guys don't plug into the factory 120V volt outlet unless they are using both sides of the 240, and then, no more than 1000 watts.