Wedding insurance covers everything that's non-refundable, and it's amazing what it covers. If your great aunt cannot get in because the airport is closed, she'll get a new ticket. If you had to cancel or postpone the wedding because you had appendicitis, the matchbooks that you ordered with the date of the wedding on it will be replaced.

You can't do it the day before the wedding. You can't take out a policy immediately before the wedding. You'd want to do it at least a few weeks beforehand.