I was an electronic tech for about 15 years until I changed careers in the early 90s. Any ET worth his salt would always completely discharge any rechargeable battery before recharging - the well known 'memory effect" of the batteries of the day as the reason. Of course this was before modern lithium-based battery technology/methodology rendered the memory effect null and void, in theory anyway.
As old habits are hard to break, I continue to fully discharge my batts as if the memory effect still prevails. Whether this practice really helps or the hurts the batteries, I have only anecdotal evidence to offer. I am still using the very first e-cig batt that I bought in November last year, a 4081 shorty. I don't use this battery extensively, but I use it daily, primarily when driving to and from work or other outings (along with a 510 mega). A friend who started vaping before I did, and is a heavy vaper, rotates three e-go 650 batts to get through the day. All of his batteries are over a year old and he has always fully discharged the batteries before recharging.
My primary vaping batteries are two 14500 that I rotate in a 3.7V box mod, a 14500 pair that I use in a dual battery box mod (3.7 @ 1800 mAh), and another pair in a vv box mod. The oldest of these batteries I purchased in January this year, and just over the past couple of days, I have noticed that one of these seems to be slipping a little bit and not holding a charge as well as before.
I know others may well respond to say I am totally and completely wrong. I know that these e-cig batteries are said to be immune to the memory effect. I am only reporting what I have observed through first hand experience.