But what if you could stack two of those 0% intro APR windows back to back -- effectively buying yourself about three and a half years of breathing room? When you're doing the math, start by assuming you can only make one balance transfer. Divide your total balance by 21 months -- that's your monthly payment. Is that a realistic number for you? If so, go with that. If not, a 42-month version can make for a reasonable Plan B. If you're carrying debt on a credit card and looking for breathing room, you alread ...