[helijeli]

I have a 12V soldering iron that I soldered a XT60 plug onto the end so I can power it from 3S packs (Could be a chicken & egg scenario here! - obvious used another iron!). (You can also buy these irons from Hobbyking). Effectively makes it cordless and means you could use it at the field.
This is a good way to totally discharge a pack - just leave it plugged in till the Lipo is totally dead. If its a 25W iron, at 12V supply, it draws around (Power = Volt X Current), 25\12 = 2amps, so a 2.2 Lipo would be drained in a little over an hour. When actually using the iron in a normal fashion and wanting to be kind to the Lipo, I have a battery monitor hanging off the balance lead to audibly (& Led display), warn me when the battery is getting low.
My mild OCD also niggles at me when having fully charged Lipos lying about. I currently am consciously aware of 2 charged ones sitting in the metal Cash box I store them in (in the back Fridge). I don't stress too much however - I know they'll get used the following weekend; I wouldn't leave them charged indefinitely, but as long as you store them in the Fridge, minimal damage is being done.
Basically. the theory is:
This is roughly how much storage capacity you permanently lose:
Fully Charged: ambient temp (25deg) - 20% per\year, just above 0 deg (fridge) - 6% per\yr.
Storage Charge: ambient - 4%, Fridge - 2 % per\yr
Temperature has the biggest impact, so as long as you store them in the fridge (don't freeze!), you'll find your Lipo life significantly improved. There are other factor too. You can significantly increase the number of charge\discharge cycles from several hundred to double or more if you don't fully charge to 4.2V\Cell - say 4.1V & don't discharge below 40%. Not very practical though as chargers are designed for 4.2V and most people want max flight times. I do however tend to land around the 40% mark - next charge cycle is quicker also and you're at the storage level if you happen to be finished for the day. Anyway lots of info online about Lipo theory if you're interested.
Funny, I think I looked into all this when I acquired my 4 $50 each 6S, 3.3 Lipos for my 550 Heli and wanted to look after them. Theyre over 3 years old now and I haven't noticed any significant loss in capacity yet. Still landing after 6 or so minutes with 40% capacity left.