Joe1,

If your Trex 450 is a belt drive, make sure the belt isn't to tight, that will rob power from the system and cause shorter flight times. 8 minute flights are pretty normal. But 12 to 14 minutes, that I'd have to see. Get a couple extra batteries too.

Also, try these throttle and pitch settings.

Normal mode

Throttle:
0, 50, 80, 90, 100

Pitch:
40, 45, 50, 75, 100

Dave