Just use them once every three months or so and you'll be fine.
I like to annoy Target Cashiers for this =)
Target Prepaid Amex
You can load it from a credit card for $5 upto $1000 with any number of credit cards, I load up $5 from each of my 20 cards just for fun, then use it to buy $100 of groceries =)
Oh now that's a good one...Lol
Before you app think... Have you done your research of the CC? Does it fit your spending? Do you have a plan for the bonus w/o going into debt? Can you afford the AF? Do you know the cards benefits? Is it worth the HP?