I switched over to synthetic oil a few years ago in everything including the genny.  Moisture can break down organic oil and it will still look good to the eye. Just one of my many OCD issues when it comes to vehicles or gas machines.  I change the oil much more than required.  Having said that, I have never had an engine failure due to oil related issues on anything.  
I keep our vehicles for many years.  10 year minimum so that I feel I have gotten a good return on my money.  I admit we don't drive as much.  My 2005 Lincoln Town Car only has 42,000 miles on her and stays in the garage.  Our 2005  Toyota only has 63,000 miles.  Our M/H has 23,000 miles and is a 2002 Fleetwood.  
Still, I change the oil in these units constantly using Mobile 1 synthetic. I'm so bad my brother gave me a case of Mobile 1 for my birthday....lol.  But, no engine failures.