OK, I just checked a bunch of batteries that have either been sitting in a drawer or a flashlight for at least 4 months, This is what I found
Rev Jims Li-ons were all about 3.8v
Blue trustfire flame 4.1
Xtar 2.45 ??? Wonder what is going on with that...z
Red Trustfire flame 3.54
2 trustfire 14500;s 3.5 each
2 HiMax 18650 batteries charged about a month ago still read 4.27 each I still think these are the best buy in 18650 batteries...
I like to rotate mine about every month or so. If not I will cycle them in my hobby charger. I bring them down to 3.2v at 800mah then recharge them to 3.8v at 500mah. Probably anal but it gives me something to do :)
One thing you need to keep in mind when storing batteries is that voltage is not always a indicator of battery stability. One time I pulled a bunch of Sanyo batteries out of a old laptop and they all read 4v-4.1v I thought I hit the jackpot! When I tested them in they put out between 6-40mah 
Charge them to 90% and keep them in the fridge using the IPX6 battery boxes from DX. Nothing lasts forever, especially not alkalines.
Read some where (can’t remember where) that NASA satellites charge li-ion to 4.05V. Claim was to get the most life out of the cells like10+ years.
well said! I do so, however, do not put the battery pack in the fridge but I keep it on the desk ..
Very interesting thread so far, I think I have more questions now than when I started it.
I unplugged my laptop at work (I use it as a desktop) and at 12:45pm it said I had 93% battery left, 4.5 hours.
I monitored it all afternoon, at 5:22pm it said I needed to charge it, only 8% left, or 13 minutes. So I was able to get about 4.5 hours of pretty heavy use, out of a 4-year old Dell over-sized battery. When new, I think it was capable of 5.5 to 6 hours of use from it. So I have lost about 25% of the original power, but again this thing is 4 years old and I've had a lot of batteries fail totally and have to be replaced in 3-4 years (camera batteries are famous for it).
Can you recondition a used Li-on battery? Is there any kind of magici charge/discharge formula that will boost capacity or performance?
wait a minute!!! does this basically say u should be thstoring bats in the freezer? i thought someone said elsewhere that id didn't make any dif.
does anyone have a voltage chart/table for various size bats resting, storage, charged?
Thanks for posting this. Like others, I tend to top off my 18650's in my Pila charger and then store them until needed. But every few weeks I do check them with a DMM. Capacity may be reduced over time allowing them to sit fully charged, but they take to long to recharge and if I need one of my flashlights, I'd rather have it ready to go.
mmh no, btw you ever read the medium-voltage on the batteries warp and can know the charge level by a proportion
For example an AA nimh(also LSD like eneloop) rated 1,2v is full charged at 1,4v empty at 1v
A lico rechargeable(most common litio that we use) is rated 3,7 full charged 4,2v discharged at 2,7v for the lico follow my(posted by me xD) table
A lifepo rechargeable rated 3,2 full charged at 3,7 discharged empty 2,5v
The values given are just guidelines
Size doesn't matter, 10440 14500 18650 26650 lico will be all charged at 4,2v empty at 2,7v, does the technology used, but there are exceptions, for example nimh 9v(6HR61) batteries can use 6/7/8 cells in series with medium-voltage respectively of 7,2/8,4/9,6 V is just 1,2v*6/7/8
I hope u'll understand something xD (comment related to my ability of write in english not by your ability to understand)
Cheaplite: Not in the freezer (well below freezing), best is in the refrigerator, which is just above freezing. It is also best to store at around 40% of charge. But remember, this is for long term storage. If you are using batteries on a regular basis, there really is not much advantage for cheap cells.