I think temp probes etc are useful ... let's look at the RC car scene, in the 1/10 touring car we really need to monitor the temp if not the engine will definately break a crank shaft or conrod because its running too lean.

We usually run the engine in the 130C (sorry I do not have it in F) range if you are being compatitive and if you want to push it then in the 140C-150C. Difference in life span? Well at about 110C it lasts about twice as long as 150C. This is info we gather from other drivers over a couple of years.

I still check my plane engine temp when I land, I want my engines to last. Temp created by 'friction' (be it due to lack of oil or bad tuning) will kill an engine.

When properly tuned my engines are reading about 230F just right after I land, sometimes with my SA72 its only about 220F only.