Keep them clean, protected, and sweat-resistant longer
IPX ratings tell you your earbuds can survive sweat; they don't tell you sweat won't slowly degrade them over time. If your earbuds ever get properly wet (not just sweaty), most manufacturers recommend wiping them down with a soft, dry, lint-free cloth. Then, make sure you actually let them air dry for a couple of hours before using them or putting them back in the case. Where you can actually extend their lifespan further is the case itself. Any soft case is basically decorative—it does nothing