I've been timing my flights with the DX6i at 6 minutes. Sometimes I can detect a decrease in power just befor the 6 min. run out. Must be the programed cutout of the ESC. I'm still flying with training gear so I'm sure my flight times will get longer when I feel comfortable removing the gear.
I have noticed that the batteries are pretty warm when the 6 min. flight is over. I'm assuming the heat is at a normal level for the 450 after a flight. I'm running 11.1v 2200mah 20C mystery packs. I realize that it's impossible to judge temperature without a measuring device, I guess it might be time to get a battery themometer.
I'll try a flight without training gear today and see if I'm still pushing the packs to close to the cutoff at the end of the 6min. timer.
Curt