Driving Range afternoon

Hit the driving range at lunch today for a medium bucket. Started out on one side hitting into the sun without a jacket and in short sleeves. Moved to the golf school side of things. There were three of us on the range. I hit most of the basket of balls with my PW/45*. I took some divots and sent a couple a bit left plus a few short and worm burners but most went mostly straight and in the 100-120 yard range. I was better at the beginning of the bucket than at the end but it was still good. I am trying really hard to bend instead of squat. That and the right distance and neutral grip are enough swing thoughts. I actually think I am ending up with the ball further from my body than before. Hit the snot out of a couple of balls with the driver. Even with the extreme spin to the right they still went about 150-180 with about 60-80 yards to the right. Hit a couple of shots with the 5W that went pretty far and only slightly leftish. Wonder what kind of conditioning I can do to build up my stamina for swinging at ball after ball? I mean besides dropping 60 lbs.