Two questions embedded here. Firstly: Do you NEED to replace your sunglasses? The answer is: No. Sun can certainly degrade things over timeit’s absolute murder on tent fabricbut the hard material used in sunglass frames and lenses, while not impervious to sun damage, can stand up to it for many, many years. What’s actually apt to cause damage to the material, such as the temples (the pieces that go over your ears), is the acid in your sweat. So, it’s a good idea to give sunglasses a fairly regular wash with some warm water and something like Dawn detergent, then to dry them with a soft cloth. Glass really IS immune to the sun, so no worries there.
The hidden question is: Do I WANT to get new sunglasses? The answer? Of course you do. Today’s sunglasses are amazingly good, with better coatings (reduced glare and better color rendition) and more rugged frame materials than ever. And, prices have held steady or come down after several years of truly excessive price hikes. Oakley’s Eye Jacket 3.0 ($130), for instance, have temples covered with stuff that gets stickier as it gets wet, so the glasses stay on your head. They also have super-sharp coated lenses and look great. Or take a look at the Julbo Reflex, an all-purpose sport shade that comes with four sets of lenses, all for the bargain price of $90. Lastly, check out the Rudy Project Kerosene ($125), which has super-tough frames and a streamlined style, perfect for bicycling and other high-speed sports. Any of these will protect your eyes from UV radiation while giving onlookers a better you to look at.