I've had two cards with 18 month interest free promotions recently. If you invest the cash you would have normally used to pay the card off, than that's a free

I've had two cards with 18 month interest free promotions recently. If you invest the cash you would have normally used to pay the card off, than that's a free 8-15% gains! Kills your credit score due to high utilization until the promotion is up and card is paid off though