Yeah I'm not surprised you didn't like the eGo Aio. Not a lot of airflow, small coils, lousy battery life.
It depends on how much you vape with regards to battery life. The capacity of batteries to hold a charge is measured in mAh, short for milliAmphours,
Since you're worried about battery life, there are some that hold as much as 3400 mAh of chrage, and will last longer than the typical ones that hold 2500-3000mAh. Go with a REPUTABLE BRAND (LG, Panasonic, Samsung) or you'll be stuck with a battery that doesn't actually hold as much charge as it says it does!