A good 27-inch curved gaming monitor should serve you for five years or more. Avoid buying the absolute newest model the week it drops, as you are paying a premium just to be first.
Wait for back-to-school sales or late autumn events like Black Friday. Last year’s high-end model usually performs just as well as the new one but costs significantly less.
That 15-month window is a deadline, not free money. If you have a balance left over after the intro period ends, the bank will start charging interest on whatever is still owed.