A previous poster alerted me to the two bonus structures offered by DiscoverCard. NB: It takes quite a bit of digging to find this info on their web site!
Platinum Specialty (Gas) Card:
Each year, earn a full 1% (5% for gas) of your first $1,500 in purchases; your second $1,500 in purchases earn .50% (3% for gas) and purchases in excess of $3,000 earn .25% (1% for gas). Transactions must be sent to us under merchant category codes 5541 and 5542 to qualify as a gas purchase. Purchases made at select warehouse clubs, discount stores and their affiliates earn .25%. These purchases and gas purchases are included in the total amount of purchases made during the year to determine your Cashback Bonus on other purchases. You will not earn a Cashback Bonus on annual gas purchases in excess of $25,000.
Ordinary Platinum Card:
Each year, earn a full 1% of each purchase made after your total amount of purchases exceeds $3,000; your first $1,500 in purchases earn .25% and your second $1,500 in purchases earn .50%. Purchases made at select warehouse clubs, discount stores and their affiliates earn .25%. With our Get More Program, you can sign up to earn 5% Cashback Bonus on purchases made at select merchants or in certain merchant categories throughout the year.
I wonder if they will let you start on one card and then take out another when the $1500 point is reached, and then a third, ...