Because once you have shown it is possible once, it means it can be done again. Why destroy a piece of history when you can destroy number 2 trying to fly it a

Because once you have shown it is possible once, it means it can be done again. Why destroy a piece of history when you can destroy number 2 trying to fly it a third time? They most likely spent the time bringing it up to the latest rev because of the performance improvements and increased reliability of the newer version. They didn't really care about how much time it took to get the second one to fly, as long as they could get it done. This was a really big milestone for their future plans, so it didn't really have a monetary or time limit.