I would continue to take them throughout the whole time- and especially after they are all replaced.
You may save the activated charcoal and Algin to only use before and after each filling replacement- and then take these daily as you chelate old mercury out of your body when all the fillings are replaced.
The rest of the nutrients I listed will only help you if you take them throughout all the days leading up to and between and after your replacements-- After the fillings are replaced -- then you begin chelating. Chelating old mercury somtimes can cause detox stresses in your body (specifically this thing called "mercury dump" where your body sees that there is no longer a large source of mercury in the body , so it then tries to clean itself by having the blood cells dump out all old retained mercury into the body for elimination.- and these nutrients will be needed more than ever at that time) so keep them on hand after all the fillings are out!