Lag is what separates Pro's from weekend amateurs. Proper lag will/should result in solid ball striking. Solid ball striking is necessary to compress the golf ball to make it explode off the golf club. Too many high handicappers don't understand compression. I am like you in that I have been relentlessly chasing proper lag technique. I have an early release, also known as casting the club. This moves kills my power/distance and promotes poor ball striking. I've spent lots of time working with an instructor to correct the problem. His favorite drill was working the small swing. The point from 3 o'clock to 9 o'clock is where the lag appears, then releases to the follow through. He wore me out on these drills.
1. Set up to address - take the club back so your arm is parallel - look to check proper club rotation and wrist hinge - head back down - fire at the ball with proper release and hip turn. Over and over. I did this with an abbreviated follow through. Distance wasn't important. Ball striking and proper release were the focus. We did the same drill, but stopped the backswing when the club reached parallel. This drill really showed which hand fired at the ball. Point here was to pull with the left, not be overly aggressive with the right.
2. The other drill we did was starting from a proper contact position - hips mostly cleared - right leg/hip pushing down - right foot flat, wanting to roll down target line - left shoulder high, right shoulder low - hands in square contact position, with right hand slightly lagging (think Greg Norman "secret"). From this position, take the club back so shaft reaches parallel and then make contact. Over and over. To execute this drill, I found I needed to move the ball further in my stance and get closer to the ball.
Both drills were to ingrain muscle memory and to exaggerate the feeling you want at contact. I've got copies on DVD, but they aren't HD. Hope that gives you something else to try. I still haven't mastered the lag! 
