I just noticed something a bit strange with my Fenix LD10. I just tried turning it on after a couple months of non-use. (As stated above, I use a keychain fauxton whenever possible.) A "fresh" battery was sitting in there for a couple months. The flashlight would not turn on at all. I took the battery out and reinstalled. The flashlight now works fine again. The memory feature must have gotten confused somehow. So, you should at least turn on your flashlight for a split second every week or so.

By the way, don't be cheap with batteries. Use high quality lithium batteries. They are so much better than alkaline. The extra expense is worth it.