Originally posted by jatrax I think the "take them out because they leak" is just a hold over from old AA technology. I have never heard of a lithium battery leaking. I never take the battery out of my cameras. I do take out AA batteries on things I am not using for a long time. I have had those leak multiple times.
Yeah. So if you are using adapter or battery grip, you might want to take them out. You should also take them out if you are expecting extreme climate, like long time of low temperatures. In that case, you should put them someplace safe - but you would put your camera someplace safe, as well! For example, in cold climate you might not have any place to store camera and gear when traveling. But in that case you can put battery close to your body to keep it warm, so it doesn't die. Would be difficult to put a whole DLSR inside your jacket. Other than specific cases like these, I would not worry. Maybe some third parties can develop defects, but I trust the originals. I only remove it when charging.
Edit: Of course, older cameras like film SLRs and rangefinders have different battery type than the modern DSLRs, so if you have those cameras, do research on their batteries. In those cases it might make sense to remove battery