Lithium Ion batteries have no memory effect, which means that you do not have to completely discharge them before recharging.
Just stumbled across this thread looking for any hint on
why they bother to have both eGo and eGo-T batteries, as so many have wondered before (the boxes for my eGo-T USBs just picked up indicate they could also come in a plain-eGo-branded variant, and lo, the Joyetech site proves they do - kind of surprised they'd bother with two SKUs for the same thing, but it sure is hard to find anything but the -T on the market loose right now anyway)...
Anyhow, posting to reiterate, as you'll find all over here, that rechargeable lithiums don't have a memory effect* but they don't like to be discharged fully - which is why every product using one has a protection circuit that actually cuts it off before you can get close to doing that. Still, the rule is that they actually live their absolute longest when discharged "shallowly" and stored around half charge -
How to Prolong Lithium-based Batteries - Battery University - so a battery monstrous enough that you're always charging it before it can blink "dead" at you may stay "good" significantly longer than one you run down to the minimal level the circuit allows constantly.
(This was certainly borne out with the m402s I started with and how I eventually wound up using eGo / eGo-sized parts! That said, the 1000mAh USB is "inching" into stupid-crazy-long territory, so if I were doing my last buy over I probably should've paid the buck or two
more for the 900mAh - different vendors - and saved the centimeter.)
*(Even NiCds don't in practice, and the bad advice to fully discharge them is actually a great way to kill them! While it's hard to find anything that actually uses NiCds anymore, anything that seems like "memory" is in practice is more likely to be a confused smart-charger. They're still used - and apparently well suited for - power tools, so per another site's analysis of the situation, "Don't try to drill that last hole!" NiMHs are less prone to being permanently damaged forever if you run them dead once, so the modern crop are a lot more resilient for household AA-type use.)