Me?

Personally, I'd say just rigorous waterproof testing and lots of drop testing. These are the primary real-world opponents lights will likely face and need to overcome.

Beware, boiling or squishing lights with lithium batteries would be very dangerous!

-john


Check the second picture down of the Ra Twisty. While it isn't obvious at first glance, this light actually has taken a lot of abuse. And not just by happenstance, either. Check out the diagram. The battery compartment is designed to help shield the battery from shock, and the lens has a gasket in front, behind, and on the outside. And the bezel is stainless instead of AL.

As an aside, I cracked the lens and bent the bezel on my Surefire L1 when dropping it from a ladder indoors (so, maybe 8-10ft) onto concrete. It still worked, but note the Twisty drop height was 20ft. The L1 is tough, but even a well built light starts to reach it's limit hitting the concrete. Even if the light itself survives, the impact starts to smash the battery with its own weight.