there is no pat answer to this. it depends on what toxins he has, where they are stored, how fast they come out, and how all this effects his current status.
it is kind of obvious that it does no good to detox mercury while ingesting it every day. your husband is basically freebasing mercury. it gasses off of the fillings and he breathes that into his lungs and injects it directly into the bloodstream. here is a good lesson in how lifestyle can effect health. the higher the temp of the fillings, the more they outgas. hot food and beverages will do this. a cool liquid diet will minimize this. also the chewing of food will generate heat via friction. much less mercury can be ingested via the lungs simply by training the body to breathe in through the nose and breathe out through the mouth.
cleaning up the body too much will start it working on the mercury fillings themselves. there is definitely a point of diminishing returns when cleanising with Amalgams in place. that point must be determined by the individual.