This is because you might have a balance that rolls over to the end of the offer period and you will have to start paying interest for it. (topcreditcardsreviewed.com)
Another perk is that Barclays Bank Delaware charges no balance transfer fee even after the end of the offer period. (effectify.com)
If you can not pay off the total balance before the end of the offering period, you will be stuck with interest rates that are more than likely going to be as high as the original cards you consolidated, to begin with. (consolidation.creditcard)