It's fine to have $0 balances --that is strictly a FICO scoring issue. The banks don't care a flip about what balance they report to the credit bureaus.
But they do want you to use the credit that they extend, so you need to keep using the cards, in order that that they aren't closed for inactivity. This can be a challenge for store cards, but it shouldn't be difficult for bank cards (Visa, MC, Discover, AmEx.)
For instance, I buy four tanks of gas a month, and I go to the grocery store 2-3 times a month. Whether I had CC's or not, I would have to do these things in order to get to work and back, and to stay alive. If these figures are typical for you, and if you have 6 or 7 bank cards, you can just use a different one for each tank of gas and for each run for groceries. Most cards post the charge on your online account by the next day, maybe two days later. If you don't want to have the balance report, that's fine --just pay it off online when the charge shows up. The card remains active, you don't accumulate credit card debt, you're paying the same amount of money via credit that you would have via cash or check, and you have gas and grocs. A win-win-win-win proposition, and your credit stays fine. In fact, your FICO scores will trend upwards over time, because having multiple credit tradelines reporting strings of clean history month after month results in steadily increasing scores.
That can be a bit high-maintenance on your end, of course. You probably don't have to use every card every month. Generally, every three months is OK, although some banks, especially HSBC/ Orchard, are pretty twitchy this way. They seem to require frequent feeding.
Banks do make money off of your purchases via transaction fees, so even if they're not getting that nice juicy interest from you, regular usage will probably keep them content. If you have any crazy-high CL's, some might wind up being lowered, but that doesn't affect your FICO scores if you don't have balances: $0/ $100,000 = $0/ $100.
Most store cards are happy if you use them every 6 months. Some don't mind if you only use them once a year, for Christmas shopping, for instance, but twice a year is safer.
If and when the time comes that you plan to apply for credit, allow one of your cards to report a balance two months before your new credit app, and then pay it off when it shows up on your statement. Do the same the second month. You'll probably get a one-time score ding for a card reporting a balance for the first time in a long while, but the next month that ding will be gone, which is why I said do it two months ahead. And the damage isn't that much unless you're up in the 800-range --maybe up to ten points --so it might not be critical, depending on where you are.
The important mind-set is to learn to look at your personal credit as a tool: what can it do for you? How can it help your finances (rewards, 0% on major purchases, simplified bill paying, lowered insurance premiums, etc.) Where might it threaten your finances (temptation to start carrying CC debt, etc.) Like any tool, it can help or hurt, so your job is to understand exactly how it works, and remain its master.
* 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