Reduce wear by keeping the fuel cool - perhaps - but it's a moot point, I have been using a sleeved TT42 GP for 12 years and it is running great!

The lifespan of an engine can easilly exceesd 10 years IF you use a good fuel (with caster oil) and keep the RPMs within tolerances. (tune for peak and then back off 500 RPM)

As to the amount of Nitro in the fuel - check the manufacturer's recommendations... they make them to run on X% nitro for their market... If you get a European engine it could require 0% nitro.

From my experiance 5% works just fine, 10% is also OK - passed that you are just burning up your money.

IMHO