Would you rather fly on an airplain's maiden flight or its second flight. For me, the wear is far less a concern than a quality control failure at manufacture.

Would you rather fly on an airplain's maiden flight or its second flight. For me, the wear is far less a concern than a quality control failure at manufacture. I want flight proven but I also don't want the flight leader in the fleet. There's a sweet spot between, "they're still working out bugs from the factory" and "the core, non-replaceable systems are starting to wear out." My guess is that's around 20 or so flights for an F9 booster, maybe a bit more.