Carry one or two rewards cards, but have two or three others in a drawer somewhere. To keep them alive, you can assign each one a recurring monthly bill or donation to pay, and have online automatic bill pay to pay the card balance. That way, you're not buying more stuff than you normally would; you're just running something through the card.
Think of cards in the sock drawer like this as investments. They're just there in the background, humming along, helping your overall money matters.
When you only have two cards, if you don't pay them off before their statements drop, it will look like you're carrying high balances and using "too many cards." (too many = both)
I have a card that I'm annoyed at that I don't want to close until next March. USAA has an EX monitoring service that costs a whopping $5.50/ month. I put this service on my annoying card, and this keeps it alive. Until I decide to kill it off.
* Credit is a wonderful servant, but a terrible master. * Who's the boss --you or your credit?
FICO's: EQ 781 - TU 793 - EX 779 (from PSECU) - Done credit hunting; having fun with credit gardening. - EQ 590 on 5/14/2007