Mr Willis is 67 years old. I suspect that any incoming attack asteroids are more than 13 years out (it just seems statistically improbable that one will show up sooner than that - I don't have any data on incoming bogies), and asking a >80 yo person to go take out asteroids seems like a plan destined to fail.
Point being, we should hurry up and create a bunch of Bruce Willis clones before it's too late. The future of humanity depends on it!