I would have thought the NAZA system worthy of the extra time it takes to set up.
Surely having an aircraft that will auto land when the batteries get too low is better than one that falls out of the sky for the same reason.
You have to remember that using a timer is all well and good when your batteries are all new but as they get older the capacity decreases. With a timer you would get closer and closer to danger levels until the inevitable end.
A good lipo buzzer is probably the next best thing but a combination of all methods, including monitoring what goes back in to each battery, has to be the best.
Just my humble opinion and experience.