this question depends on application and how you are tuning
I ran a .28 sport engine for 2 race seasons before the crank bearing gave out.
Always want to see smoke and don't run the engine too lean
I have had the same engine in my Losi LST which is a 427 Mach ported and polished for more then 4 years now.
About 3.5 gallons or more and it still runs strong
I have been using Odonnells 20 or 30 %
this fuel has always been my choice I have tried a bunch of others but never had any luck
also always keep the air filter fresh