Clicker training - voluntary "heel"

A funny thing happened when I was walking the dogs. I had decided to use clicker training to teach Lucy to stay closer, since she mostly gets to be off leash. I started by clicking every time she looked at me, and she would come running to get the treat. I also clicked every time she approached me. Gradually she started hanging around very close to me and I was having trouble not using up all the treats before we got home. So on the next walk I only clicked when she walked at my left side, then only if she also looked up at me. Gradually I waited for 1, then 2, and up to 5 steps walking at my left foot and simultaneously looking up at me before clicking. That day she walked at "heel" voluntarily for hundreds of yards. When I teach "heel" it normally takes major concentration just to keep it up for 10 - 20 yards. With Lucy I used to pretty much have to hold the treat in front of her nose the whole time. The next day I started increasing the distance that she has to walk at my left side while looking up at me to 20 steps. I then varied between 5 and 20 steps and she still spends a lot of time "heeling" voluntarily on our walks. I've even tried left and right turns and changes in tempo. She "heels" like a champion. Now I have added a new aspect. If I feel her body against my leg, I immediatly click and treat. Otherwise she has to walk 10 - 20 steps before I click. The idea is gradually to get her glued to my leg for "heel" excercises. On our walks it has all been voluntary, and probably I will keep it this way. However I plan to add the command on our training sessions soon.