A good ultrawide monitor changes how you work. It gives you the screen real estate of two monitors without the annoying gap in the middle. If you buy a high-resolution model now, it should easily last you five to seven years before the tech feels old.
New monitors usually drop in the spring, which makes the back-to-school season perfect for picking up last year's flagship. The hardware hasn't changed much, but the price usually drops significantly as retailers clear out old stock.
The 0% for 18 months on purchases and balance transfers from date of account opening isn't a gift; it's a deadline. If you still owe money when those 18 months are up, the standard interest rate kicks in on whatever is left, making that monitor much more expensive.