Here I go over some very simple and basic mods to extend flying time by up to twice stock. Keep in mind these results are highly variable, and I typically fly lightly with few stunts. I tend to fly with maximum forward pitch, lowest possible throttle, and mostly yaw for turning. Those changing altitudes and performing tricks will see reduced power output. Same goes for windy days.
To upgrade my battery I simply use a 2800mAh battery instead of the stock 1200mAh. Quadcopter connectors are often similar. In my case, JST connectors were used. I recommend this page for more info: http://skypixel.org/post/59231840022
Finally, fly safe!