A solid high refresh rate monitor should last you five to six years, so you want to buy right the first time. Back-to-school sales in August are a prime window to grab one. Monitor manufacturers announce new displays early in the year, which means last year's high-end models get marked down heavily right as summer ends. You get near-flagship performance for a fraction of the original price.
If you want to grab a $500 display without wiping out your checking account all at once, you can spread the cost over time. Pairing store sales with the Discover it® Cash Back card gives you room to pay off the purchase month by month without owing interest.
Keep in mind that a 0% intro APR window is a strict deadline, not free money. If you still carry a balance after 15 months, the regular interest rate will apply to whatever is left, so stick to your monthly payoff routine.