I guess I should clarify now that I've been jumped on. I've had my flywheel resurfaced once and that will be it. I don't think it's wise to do on a stock flywheel but this is simply my opinion. I'd rather have the assurance of a new billet steel flywheel. My point was that machining (flywheels, rotors, engine blocks) thins the material. A flywheel will warp as a result of heat cycling and when you resurface it, various areas of the material will be more thin than others. For example, if you took something flexible, say a thick piece of foam and made it "warp" in the middle. Then took a knife and shaved the surface until the warpage was gone and you had a flat surface again. Well there are a few areas now that are thinner than others.
No biggie here. If someone wants to resurface their flywheel 2, 3, 4 times....that's fine with me. Just putting my .02 in like everyone else.