Nice goin' on the eGo! I still use 3 eGo batteries myself
Yes, the larger the battery the more likely it'll last longer in between charges. Personally, the eGo is just fine for me. If you're tired of the battery dying at inconvenient times you could always opt for a larger one
I would recommend stocking up on some atomizers as they're the heart of your vaping device. Personally, I recommend Ikenvape atomizers for a number of reasons.
-They're very reasonably priced ($8 a piece)
-They're primed with a flavorless PG liquid (instead of that NASTY primer crap you have to burn off before vaping)
-They're super beast (I've had one LR for 3 weeks and is still hitting strong)
-They just make the juice taste better (In my respective opinion, of course. Ymmv)
Congratulations!!!
Edit: If you're a cartomizer user (which I am not), I've heard nothing but GREAT things about Ikenvape's cartos
Cisco brand atomizers are also fantastic I hear from avidvapors.com