Mine are replaced every 3-31/2 years. I ride a lot and sweat a LOT too. Over time retention straps fray and weaken, EPS (the styrofoam stuff) degrades with hair products, sweat, fumes, et al, rivets and anchors rust.
Do they HAVE to be replaced? Probably not as an absolute but all the things have to be considered and I feel like I get more than my money's worth. This is an oil, tire, octane, type question in most forums.
My noggin is worth it and keeping it inside the dates gives me a warm fuzzy feeling it will be there for me if ever put to the use it was intended.
Some people go their whole life wondering if they made a difference, Marines don't have that problem.~ Ronald Reagan
2012 XCT, AFR+ Gen 4, Lloydz air filter. I don't equate noise with power.
I ride with the Force.