An exended warrranty on your KM 5D?
Just my opinion.
First, extended warranties are usually a waste of money. The warranty company is betting that the device will last, you're betting it won't, they hold the money, and they decide who wins.
Just my opinion.
Second, if nothing goes wrong with the electronic parts of your camera in the first 90 days, most likely, nothing will go wrong with them for several years. And companies have been making the mechanical components of your dSLR (focal plane shutter, mirror, etc.) for decades, and for people that demand reliability. So digital cameras are probably some of the more reliable things in your house (except, maybe, the doorknobs.)
Just my opinion.
Third, KM and Sony have extended the warranty on the 5D for a number of known problems (see the
Konica Minolta / Sony Alpha dSLRforum), and chances are good that will handle any problems you haven't experienced yet. The bad side of that is that once they've run out of parts to service those cameras that are experiencing those known faults, nobody, not even your warranty company, will be able to fix your camera. So the extended warranty probably won't do you any good.
Just my opinion.