Part of my point about inspecting both the sling, & the rope, is that it takes quite a lot of protective material to fully stop all of the Sun's rays. Several feet of lead will (mostly) do it, ditto several hundred feet of
water, etc. But then again, there are cameras that can see installations built inside of mountains... from space.
Witness the whole Ford Explorer rollover issue a decade+ ago. It was due to the use of PBO (Zylon) as belt material in their tires, instead of
steel or Kevlar. With the PBO failing, despite the it's being fully encase in rubber, plus a few other materials in addition to that.
So Lifeslings are vulnerable to Sun damage too. Regardless of the type of case used, or how well they're packed into it. And it's also why a more UV resistant, positively buoyant line, probably wouldn't hurt either. I'd also be tempted to coat any of the line that exits the case with
Maxi Jacket, covered with webbing or no.