SpaceX's claims aren't extraordinary though, they're actually rather mundane. They've run the engines on test stands through their paces and figured out their l

SpaceX's claims aren't extraordinary though, they're actually rather mundane. They've run the engines on test stands through their paces and figured out their longevity. They've flown several flights using reusable test vehicles. They've even flown part of the operational flight profile with live stages during actual missions. To be honest it would take something coming out of left field to throw off their reusability plans at this point. At the end of the day the engines just haven't been exposed to very significant adverse conditions during a normal flight, there's no reason to assume the durability would be so much less than on the test stand. More so, the stage is mostly just fuel tanks, engines, and landing gear. There just aren't that many components, and there isn't much opportunity for something to go wrong. They fill and drain the fuel tanks repeatedly, there's no reason to assume they'll suddenly stop working after actual flights. And the overall structure of the vehicle is more than strong enough to withstand several launches and returns. In terms of results SpaceX achieving reusability will be a big deal. But in terms of the prospects for reusability, the vast majority of the unknowns have now been filled in, at this point it would be more surprising if it didn't work than if it did.