I went 3 months paying for gas, groceries, miscellaneous stuff, and beer - not a peep out of Discover. I then used it to charge a livery service from the town to the nearby big city airport to fly home for Thanksgiving. THAT they noticed. They called the house, wife explained the situation to them, said "yes the charge is valid" and Discover went away. Used the card for another 4 months without hearing back from them.