My Xtar WP-2, with three amp settings, started not charging up one of the batteries of set, all the way, when light green. It was set on 0.5amp. If I put the lower charged one back in it would then charge it up all the way. I moved it up to 1.0 amp and it's charging correctly. I'm using a little do-hicky Scott sent to me to measure batteries. It is very accurate. (The Xtar WP-2, like some of the other high end chargers, will bring a battery out of "too discharged" state. Many of the chargers can't do that.)
On the other hand one set of AW IMR 18350 batteries I got in June '12.... I was getting less than 2 hours from set from beginning. It was due to one of the batteries of set being faulty from the beginning. (I switch battery position every ml of juice or so to keep drain on batteries more equal.) That battery has now been recycled and it's good partner is waiting for a mate when, and if, another battery of any set should get weak. I probably should just order one new AW IMR 18350 to make up a new set from the good one of set. The good battery, of set with bad battery, didn't get very stress as I used it max for an hour or so, when I used that set.
I have about 7 sets now in rotation with mostly me using them but I always have one or two WWGs going round the clock. I've already tossed (recycle) a couple of sets from late last year as they were getting worn out. My oldest ones are from March 12 now. A couple are showing reduced use time but not enough to toss them yet.
If a properly charged set gives less than 2 hours it's time to retire them. Most of my ERA coils (and soon to be REOmizers, Hornets, and in January Surface) are between 2.0-3.0 ohms. At near 3.0 ohms I crank the voltage above 5.0.
I'm getting good use time with the Joytech 2.7 ohm attys. Voltage near 5.0. My juices are light medium color, no tobacco, but pretty sweet butterscotch/FSUSA Applewood, ~50/50 PG/VG, 18mg.
I vape 1.7-1.9 Smoketech cartos at a little above 4v and usually get almost 3 ml through them before changing batteries. (I turn off the VVs when not in use.)
Hugs, Feisty Alice