Occasionally I hear about pressure buildup from venting, and who knows how often a simple valve could have prevented an explosion or rupture of a case. I think Maglite's solution on at least some of their flashlights is an O-ring with a triangular cross section that allows venting from inside out. I don't know if such O-rings are available to other manufacturers, but I know that umbrella valves like Pelican uses are. A company called Minivalve has a form on their website for free samples of "over 50 different miniature valve components." Just drill a hole and push in the valve. It may require a flat spot on the body of the light. Why not offer a light with an umbrella valve? Waterproof cell phone manufacturers should use them too. Or maybe they do but I never heard about it.