I wonder if the Duracells might be kind of like the rechargeable Energizers, which are so hit-or-miss performance-wise that they can't be depended on for long-term use (in my experience).

I have just a few of the Duracells, and they've been exceptionally good performers. Been using them for close to a year now with no signs of anything but solid reliability (hold a charge well and run for a very respectable amount of time in whatever I use them in).

I'd think that Eneloops ought to do just fine, but probably won't get you the run time of the higher-capacity batteries. I have a couple of sets of Eneloops, but since I also have the Powerex and Duracell batteries, I've never had to use them in my L2Ds (except for a couple of short amounts of time that didn't really test the batteries much).