There is no reason to go to 50% for the first few flights. Lipos don't work like that. Just fly to 30% or home icon says come home, by the time you land you'll be somewhere between 25-28%. Doing this, I get 23-25min flight times.
It's recommended to deep discharge your battery(s) every now and then, I do this about every 10 flights on each battery. DJI has instructions on this from the manual on how to do it. (Found on page 19 of the user manual)
Two ways to do it,
A) Keep the bird on after a flight until it gets to 8%, you could keep the blades on idle if you wanted to speed up the process some
B) Fly at 3 - 5 feet, and just wait till you hit the 10% auto land, I've found if you let it do it's 10% auto land from 5 - 10 feet it's dead on 8% after it shuts down.
This will keep your battery(s) with max flight time over the life of the battery. But I agree with tcope, it's perfectly ok to fly to 25 - 30% without any issue at all.
