Not sure if all CCCs do this, but if it's dormant for too long, they may close the account. I believe it's best to charge something small (even pacck of gum) to the cards at least every 3 or 6 months, then PIF, just to keep them active so they don't get closed. Just my opinion, of course YMMV
Doesn't hurt to keep them around, but do make sure you make a purchase-- even a small one like a pack of gum-- every few months to keep them from suffering credit line decreases or being closed altogether. A safe move is a purchase once every three months, since some issuers are pickier about inactivity than others. I had a Target Visa that sat dormant for close to three years before they closed it. Oops.
EDIT: BrokaToe beat me to it. Not sure why it took me 20 minutes to write and post that... oh well. 
There's also the potential that FICO scores inactive tradelines differently. No idea when this becomes a factor or after how long but it seems to be pretty common wisdom.
It's absolutely worth using any card you have open occasionally. Personally I just tag one random incidental expense on every card each month, either an autopay bill, or I just carry it with me for breakfast or lunch one day.
@Revelate wrote:There's also the potential that FICO scores inactive tradelines differently. No idea when this becomes a factor or after how long but it seems to be pretty common wisdom.
It's absolutely worth using any card you have open occasionally. Personally I just tag one random incidental expense on every card each month, either an autopay bill, or I just carry it with me for breakfast or lunch one day.
I'm curious about this. I'll notice it listed on SW when I have a balance increase on a dormant card, it will note that a dormant card is now being used. I wonder if theres any impact fico point wise.
Does the inactive card have an annual fee?