My 'walking around' and 'stealth' setup, SMALL, lasts most of a day or 3+ hours heavy: eGo 650mAh batt, ego cone, Boge 2.0 ohm cartomizer. Mine is all stainless, looks cool with any drip tip, definitely won't leak. I'll sometimes hook it up to a lanyard.
Walking around a mall, ran into one of those kiosk shills - when asked if I smoked, pulled out my setup - blew her away.....