What I wrote before is pretty much standard for the Cutler Protocol. I would keep in mind that there are many sources of heavy metals, so it's possible you have others in your body too.
Less heavy metal would mean you probably won't need to do your chelating for very long. I would continue until your body tells you it doesn't need it anymore. I would suggest a few months at least. It depends on you. Every body is different.
Do you take DMSA too? DMSA is an important part of the process. ALA doesn't do a good job of removing the metals by itself.