I found an old AA powered LED bike taillight over the weekend with 4 Duracells in it, dated "best if installed by Jan 2002". No leaks, and they test higher on my battery meter than any of the 5 samples I pulled out of a new brick of 24 Duracells I got at Home Depot about a month ago. WTF! I guess they changed the chemestry somewhere along the line, because the new ones SUCK! I put 2 in my TK20, and 1 in my Quark AA, and I can tell the difference in both lights.
Funny you should mention it.
I just broke open 2x4 pk. D Duracells with a 2002 date on them and 1x4 pk. Energizer Ds with a 2004 date on them. I got them all on sale back in the lateish 90s for my 2x6D Maglites, but I don't use those lights much.
Of the 8 Duracells, all were over 1.54v except one, that read 1.28v, so I pitched that one. Of the 4 Energizers, all tested over ~1.54v, but one was leaking slightly, so I pitched that one.
I don't know how long they'll last in the MLs, but I was surprised that these batteries, which are 10 and 8 years past their expiry date, were mostly all good.
Chris