RE: Neoprene, Tygon, and Viton UV Resistance
I've had both Hayes black seamless neoprene, and Tygon deteriote, when both were well covered under cowl. Two years is much too long to go without changing it out. The Hayes neoprene became perforated with dozens of tiny holes that eventually opened, and sucked air. The Tygon became hard as glass, and just broke. I don't think that UV is the problem, it's just that two years is much too long to wait to change it out.
Ed