Why not go for a real mod instead of Janty's gimmicky made in china junk , the ego may last longer than a standard 510 battery but not longer than say a good Mod ie: Adaptever , GG , Silverbullet ,Prodigy, Chuck.
These devices offer more options and are almost indestructible . I have never tried the ego it looks cool and slim but with the proprietary batteries and such I'd stay away from it personally and the switch is just bound to fail eventually leaving you with a worthless piece of junk .
The other mod devices are a little bit more costly than a chinese toy but will provide you with a longer life span and less trouble more vaping .
Just my Opinion , Tommy
I have a chuck, and a bartleby on the way. I just happen to like the way this looks, and like the battery life. I'm not really going to walk around in public with a chuck (far too big imo). And I'd like a backup if my bart goes dead. For 20$, I'd say this battery is a steal.