What does “120 Night Low Price Guarantee” mean? Caitlin Bagnall March 30, 2017March 1, 2018 Mattress Firm’s “120 Night Low Price Guarantee” promises we will beat any comparable mattress prices. If the mattress you buy from us goes on sale here or elsewhere, we’ll pay you the difference for up to 120 nights. We’ll even beat any competitor’s price by 10 percent. Just let us know.