My setup is just like yours, Scott. It works great and has been working this way for years. I love the Vapor's digital temp readout, and its yellow and red temp warning lights. It really lets you monitor things when the trail gets slow and gnarly or when you're trying to stay on top of deep sand in a wash for some distance. I actually believe the stock system is very capable of preventing any damage to the engine under just about any trail condition, but I think intervening preemptively in some trail situations before the fan automatically kicks in is better for oil life, gaskets, seals, hoses, and most other engine components.

There's also the issue of "heat soaking" at fan kick-in temps. It's harder to bring the temp down from those higher rates, and when you kill the engine while it's in its higher temp range, it shoots up even higher. Engines need a certain temp range to operate at the best efficiency and power output, but you can lose a little...very small...amount of power at the higher temps before engine damage levels are achieved. I have a fairly high mileage KLX with a 300 cylinder installed. Valve wear/adjustment, oil consumption rates, and other wear factors over time have shown to be almost undetectable. It's pretty much due to good maintenance and service attention, but I also believe that maintaining more moderate engine temps with a manual fan switch have contributed to this too. My KLX has been operated more like an actual off road dirt bike than a commuter/pavement bike, so it hasn't really been babied.

Some people don't want the issue of monitoring a gauge or turning on a fan, and that's fine. I don't think this is one of those mods that is required, but I do believe when properly used it's better for the overall operation and life of the engine.