As I said before, if you're rich, why not.
But if you have to borrow the money to do it, it's very risky.
The problem is that you're holding the bag... the airline has no leverage in you.
So if they change their mind or change their plans (that happens all the time), they can just say 'sorry, things have changed', and you're left holding the bag.
If it was a bond situation, it would be okay because the airline would have something invested in you... but this is not that kind of situation.