You spend a third of your life at your desk, so an ergonomic mesh office chair is about protecting your back for the next ten years rather than just replacing a piece of furniture. A good mesh chair keeps you cool, supports your lower spine, and stops you from slouching by 3 PM. When you buy once, you stop wasting money on cheap foam chairs that sag after eighteen months.
January is the absolute best month to buy because office furniture brands drop new inventory and clear out last year's stock. Last year's model usually has the exact same ergonomic adjustments and mesh quality as the new one, just with a slightly older base color or box design. You get the high-end build quality for a fraction of the cost simply by letting the calendar work for you.
Remember that the 15-month intro window is a strict deadline, not free money, and any remaining balance left on the card when those 15 months end will get hit with standard interest.