I'm sure it's been asked before

I'm sure this has been addressed before, but I'm just looking for a simple, common sense answer if there is one.  I just want to know how long I can run a 912iS on LL before it destroys my valves, cylinder walls,spark plugs.  I'm not a combustion engineer nor a mechanical engineer.  If I change the oil and perform the other maintenance at the recommended intervals for the iS, what is is going to do the engine long term?