"Maintenance free" just means disposable
Any mechanical device can and does wear. With most all the CB hubs I've dealt with there's no real adjustability of how much cog rotation is required before the brake engages. The cog/ring ratio does effect this but that's a constant. So as surfaces wear it takes more cog rotation to bring together the internal parts. Additionally if the surfaces that rub/roll against each other are not lubed then both greater wear and less easy function will follow.
Does SRAM offer servicing instructions? Seems to me that a tear down, cleaning and relubing on reassembly would be a good thing to do. Andy