I understand why nonflashaholics use nonregulated headlights with alkaline batteries in caves. I would too. In pitch black caves, runtime is way more important than brightness. Your eyes can eventually adjust to using less than 1 lumen. Alkalines give the longest overall runtimes of all battery chemistries. Lithiums maintain a higher brightness longer but overall runtime is usually shorter. Rechargeables, for the most part, don't work well in cold temperatures and caves tend to be constantly cool. Rechargeables also don't last as long as alkalines in this application and can be damaged if drained too far. Lithiums also have the threat of venting and exploding with flame. The last thing you want is to be deep underground, when your exploding flashlight seals you into the cave, leaving you with poisonous gas to breathe in, and without a light to see. Sometimes, caves drip water and can get everything wet, so you'll want a waterproof light with a long enough runtime so you don't have to change the batteries until you're out of the cave.