Nitro does not reduce engine life.

It does change the ratio of air to fuel, change the temperature of combustion, and that can change the timing of the combustion wave, and change the amount of heat carried away by the exhaust. All of these things have an effect on an engine that is set up to run 80/20 fuel.

Amounts of nitro in the fuel under about 30% nitro can often make setting the needle valve somewhat easier. It often broadens the needle response. But if you're used to setting the needle for 80/20 fuel, this doesn't matter much at all.

Nitro sometimes works better with an igniter. I think it was propylene oxide that we used. But we used very small amounts.

We sometimes encountered engines that ran well on 80/20 that didn't on nitro fuel. Changing the compression ratio usually restored the good running characteristics of those engines. Matter of fact, when we changed the nitro content measurably, we often had to swap in or out a head gasket or two.

For sport R/C flying, I use 10% nitro year round. Higher percentages simply aren't worth the expense. I was using 5% but the LHSs quit stocking it.