@rapaleeman
Thanks for the detailed response!
Holy crap, you're experience differs wildly from mine, blimey. Also occurs to me, my numbers are all off and actually even WORSE than I thought because I forgot the JPA is 1700mAh, not 1500mAh as I stated (I previously had a Helium 1500mAh which I returned and now have the Air, hence the confusion).
So, by that estimation, I'm getting only 1,245mAh charge out of a 1700mAh battery....meaning my JPA is utter trash, lets face it. Dunno whether to return it as I'm from the UK and would have to pay shipping, probably another £10 (cost me that to return the Helium). Damn.
I'll do a bit more testing and see what happens, but everything points to my Air being a piece of junk ;_:. Whilst jailbreak may make some degree of difference, can't see it being that significance. On the plus side, like I said earlier, it IS more than enough to get me through the day (typically use about 150% give or take). Hmm.