(Image credit: Birch) We've hunted down the best deals on some of a favorite mattress toppers, so you can give your bed a spring re-fresh for even less. Take the Casper Comfy Mattress Topper, now down to $139 for a twin at Casper in a final sale. Fair warning: sizes are selling out fast, so this is one deal you’ll want to jump on sooner rather than later. The best mattress toppers can boost the comfort of your existing bed, provide cooling comfort and back pain relief. We're always on the hunt for the best deals and discounts on our favorite models — and these are the sales we've handpicked this month. If you're not ready to splash out on one of the best mattresses of the year, a quality mattress topper can make all the difference. Grab one now for less while sales are going strong. This month's best mattress topper deals Mattress topper sales FAQs Are mattress toppers worth it? So, do mattress toppers work or are they just a waste of money?…