I can't really say how the batteries perform over a long period as I only used that battery for a couple of days, just to make sure it was OK - I re-charged it a couple of times and it appeared to charge very well, I was using my old Gamucci charger and it certainly seemed to get a better charge than the Gamucci batteries. (which are crap anyway ....!)
With the above reservations I'd say that that David's batteries are as good as any of the better quality makes.
The lithium batteries presently used in e-cigs are not really up to the job anyway and I'm sure that before long something much better will be available from all the better e-cig makers - at the moment, AFAIK, if you want better batteries, the only options are Trog's 'Screwdriver' or a home made lash-up like I'm using at the moment.
As soon as the weather gets a bit warmer, and I can get back in the workshop, I'll be making something for myself that looks a bit less like an IED and a bit more like a medical inhaler.........as I'm still finding that the 'ban everything' brigade still regard e-cigs as the devils work.
Personally, I'd love to be p1ss1ng them off at every oportunity but at the moment I'm thinking "what they can't see, they can't complain about" When e-smoking is accepted for what it is, i.e. a much safer way of getting our nic-fix, we'll all be able to p1ss 'em off, 'til then, better safe than sorry....
Barry
PS - the Missus has just agreed to buy me one of Davids new, extended sets for Christnas - I shall be ordering it today............ :0)