A new mattress changes the first thing you do every morning and the last thing you do at night. Pick the right one and you sleep deeper, wake up with fewer aches, and stop dreading bedtime. Pick wrong and you spend a year tossing, flipping, and counting down to a return. The mattress is also one of the few big home purchases where timing can save you real money, because the industry runs on two predictable sales windows every year.
Presidents Day (mid-February) and Labor Day (early September) are when retailers clear old floor models to make room for new inventory, and that is when you will see 20–40% off name-brand mattresses. Plan around those weekends, get more than one quote, and the same mattress that costs full price in March can cost a few hundred dollars less during the right long weekend.
The honest part: 0% for 18 months is a deadline, not a discount. If there is still a balance on the card when month 18 ends, everyday interest starts landing on whatever is left, and the rate you will pay is the card's regular APR, which is usually high. Treat the 18-month clock like a real due date and pay it off first.