brshooter:...
I am a big guy. 6'1" and 260 pounds...My instructors said that air consumption can also improve with dive experience. They said your skills increase and you become more comfortable and relaxed underwater...
Your instructor and the advise of several members here is correct. Being a big guy myself, (6'5", 255), I can assure you that, with more confidence, less air will be used. Just 3 or 4 weeks ago, I made a 71 minute dive in Ft. Lauderdale (shallow 30-35' depth) and had about 750-800 PSI remaining. Keep at it!