Alkaline batteries have vent holes too. They're hidden, but they're there, just in case, for the same reason.I will never install 18650 batteries in a closed metal tube ( torch light ) - there is a reason why these batteries have vent holes in them.
What's your concern about a metal tube? If something were to go wrong (unlikely, but possible), wouldn't that be the best place? The most likely problem (alkaline or li-ion) that's related to a metal tube is that the battery would swell or leak and you couldn't get it out of that metal tube -- so a ruined flashlight, maybe, but any mess is contained. Note that both 18650 and alkaline batteries are basically metal tubes with vent holes as well.
They do not get hot while charging unless you're abusing (ruining) them. They barely even get warm. As for discharging, that's your emitter that's putting out all that heat, not the battery. (Even the best LEDs nowadays are only like 14% efficient, which means 86% of the energy gets turned into heat.)18650 can get really hot while charging and discharging
(The battery does put out a little heat, yes, but even the current if it's enough to drain the battery in one hour (a 1C rate) the battery temperature will only go up by a few degrees at most.
NiMH cells got hot during serious fast charging (charging in 15 minutes or less) but that doesn't happen with Li-ion/LiPo batteries charged at a 1C (full charge takes an hour) or lower rate -- at most they get a bit warm. Alkalines have a higher internal resistance and so they'll get warmer than the 18650 rechargeables at the same current.)
Neither are alkalines.and quality wise, they are far from being completely safe
Yes, I already covered that. For a short trip, you can easily carry enough precharged batteries. For a long trip, I'd probably want a dynamo. But what about your Magicshine? (Probably with it's 4x18650 cells in it's battery pack, I might add.)Another thing is that on some of my trips I can't recharge my batteries ( no stores or gas stations + what's the point of sitting for hours just to recharge batteries ;-)
It may be the right thing to do with alkalines -- but I'd rather just go rechargeable and skip it entirely.And about tossing batteries in the trash - Dec. Consumer Report just said its OK to do that... I don't agree with that...