The Fox 35 test is quite well known but the only first hand reference to it that I know of is over at SSW buried deep in the past but I'll see if I can find it. Basically, Duke Fox set up one of his engines on a test stand and hooked it up to a monster fuel tank. The engine would be started every morning and stopped when the factory closed each night. This continued for 2000 hours when he stripped the engine to check it out. The engine was in such good condition he figured it wasn't worth the effort of going any longer. Of course, he was using his own fuel that's the standard brew for a Fox 35 with 29% castor but the corollary to this story is that he also took a Fox 35 to see how long it'd last on normal RC fuel. It was ruined within minutes.