I've been involved with nitro RC's for about 25 year , most of my engines are 10 year old or more ,an they all still
have good compression.
Most of my engines never have a fine tune ,however , once a descent tune is on them ,I always keep the heat down
on them ,an always ran them a little on the rich side for safety measures ,an always used a good quality fuel
with a high oil % content!
I've used several different brands through the years :Byrons ,Nitrothane ,Towers an others ,my last Gal. was Torrco fuel ,
but always made sure they had a good oil content ,I've always use 30 % nitro ,my engines don't like 20!...
I've been involved on tons of RC forums for the past 15 years ,an learned a lot from other forum folks an RCer's!...