Although I have never tested it I agree with Henry that addition of extra sulfite to Part A will probably make it go bad faster. Beside, for the most part I don't think that killing the stain is a good idea since it is mostly beneficial with most subjects. The best way to take advantage of this is to add the sulfite directly to the working solution in amounts of from 5 grams per liter to whatever amount it takes to completly kill, which should be around 10-15 grams per liter.
If you want less stain with Pyrocat-HD as a general rule you could always double or triple the amount of metabisulfiite in the stock solution, and this would actually increase rather than decrease its shelf life. When you mix the working solution in water the metabisulfite converts to sulfite.
You can get the same result, i.e. less stain and more energy, by adding ascobic acid directlly to the working solution. Again, will have to check my notes but as I recall this works like sulfite with about 1/5 the amount.
The ability to control the stain and the energy of Pyrocat-HD with very small amounts of sulfite or ascorbic is a pretty powerful tool.
Sandy King
Bookmarks