10-15 cards, I'm not really sure as most of them have a zero balance. Most of the cards were opened to takes advantaged of the 0% balance transfer offers. Even with a 3% it's still better than paying 15%. As for suggestions, just keep paying your bills on time
God damn, how do you keep track of all that? In Canada, they'd never give you 15 cards, unless they were like $1,000 limit each. They look at total credit potential. So if you have 15 cards with 10k limit, then you can potentially do some serious damage by draining all the cards at once.