You are buying these to block out airplane engines and train noise for the next five years, which means you want a set that lasts rather than a cheap pair you replace next year. Premium audio gear doesn't change overnight, and waiting for major holiday discount windows usually drops the price on the exact model you want without cutting build quality.
Tech companies drop new flagship models every fall, meaning last year's top-tier headphones are often discounted during holiday sales while offering nearly identical sound and noise-cancellation. Buying the older version right as the new one hits saves you real money on hardware that will still sound great for years.
Remember that the 0% intro APR for 15 months on purchases and balance transfers is a hard deadline, not free money, and if any of the roughly $350 balance is still there when the window ends, deferred interest will hit your account hard.