Forgive me if this has been asked, if I use MTM certificates, but then cancel or reschedule the flight, do I lose them? Do they transfer with the ticket? Do they come back to me?

I rarely travel routes that offer Mint, so I am inclined to use them for a BOS-LAS trip this fall. But it's possible I might move my date by a day or two. If I use them now, what happens if I change the flight?