My adventurer went dead on me during my last hike. Even though the batteries were unused, they had been in the unit for several months. When I got home, I did some checking with my meter. The thing draws .02 mA continually. There is only 129k ohms(if I am remembering correctly) resistance between the positive and negative terminals. I am not sure how long it would take to drain the battery enough so that the steripen won't work, but the batteries certainly don't have to be all the way dead.
Major design flaw.