Hi Hodge, 
I think your RC experience is going to come in handy with e-cigs.  
A mega batt would only add on maybe 1-2 hours on top of you regular batt. If you can mod a 2100mah batt, I think you'd be set for the day (or two  ) 
The eGo is 650 mah and it last me 10 hours at work.