I was loading 500 a month via DD to 2 Serve cards with different names and addresses registered. I was periodically using each of them for (very small) purchases. I set up a couple of those little side "savings" accounts to park some of the money. And I tried to keep decent sized balances there instead of loading and clearing (as I did with the cards I had previously in my name and my wife's and lost). All of this extra work and both were shut down at the same time.
I believe that if you don't use the card for significant purchases (which isn't good for your miles/points) and fail to look like you are fairly scraping by you aren't going to keep your card.
Some folks have a system where they use the card (recklessly?) for a couple of months, close it before AMEX does, then open a new card and repeating. Anyone? Is this still working for those doing it this way?