I bought the 4lb powder and take a teaspoon in water once a day in addition to using it in the toothpaste mix. I am not even half way through it and I am well into my second month with it.
It does seem to last a while. I am using it as part of my detox protocol. Once I feel comfortable with both my physical condition, including health and weight, I will probably reduce my usage, other than the toothpaste, to those times that call for its use.