I don't take them apart unless they are broke or getting so low on power that it's time to rebuild.

I've personally never worn one out. I did rebuild an OS46FX that was given to me by a friend. He wore it out in the first gallon because he wouldn't listen to me and kept running it stupid rich during the break in. He never could understand why it wouldn't turn a 10-6 over about 8000RPM.

I replaced the internal parts (piston, ring, cylinder, rod, wrist pin, bearings) with the ringed heli parts (OS46FX-H) and slapped a full tuned pipe on it. YEEHAW!! Cost me way too much $$--but it was a runner after that.

IMO--tearing an engine apart unnecesarily is not a good idea. Keep it clean and run it on decent fuel. If it runs good--don't screw with it.