Need more information from you, i.e., 3S or 4S batteries? prop sizes, your flight takeoff elevation above sea level, outdoor temperature etc.,
I get around 15 mins with:
F550 c/w WKM, stock DJI 30 amp ESCs, NTM prop drive 35-30 1100KV motors, 10x5 Graupner props, Futaba R6208SB receiver plus...