Sure, you can fly it down to probably 10% and get an extra minute or 2 maybe, but at 10% your battery alarm will be going off and somewhere between 10% and 0% it's going to automatically land.
It has more to do with discharging and recharging the battery. Lipo batteries do not like to be discharged all the way to zero; your battery will start getting to where is discharges at a higher rate. (shorter flight times)
