You'd probably be better off putting the money you would spend on full cover in a bank account and letting it sit until you need it. The amount of money you'd get should anything happen after they take the excesses out would be peanuts (they'll cover it for next to nothing as well)... plus they'll be asking you to pay a very decent chunk of the car's value every year.

Different circumstances, but if I did the same, I'd have 2/3rds of the car's value sitting in an account after 2 years. Plus you get to keep all the good bits and pieces on the car should anything happen.