Walter Cavanagh has 1,497 valid credit cards — all of which amount to a $1.7 million line of credit. Currently, he holds the record for the most credit cards and for the world’s longest wallet, which stretches 250 feet, weighs about 38 pounds and can hold 800 cards. But he keeps most of them in bank safe-deposit boxes. The “Guinness Book of World Records” gave him the title “Mr. Plastic Fantastic,” and he has been in the book every year since 1971.