There are only two times I find myself playing near the edge of the balance adjustment. The first is for welding pre-polished treadplate, where I want to have the cleaning band as close to the weld as possible. This makes for an easy to polish weld. The other is when you run the machine at the very limit of it's capability and need all the extra penetration you can get, and have meticulously cleaned the material. Much more often I find moving more towards 50% for things like castings with lots of impurities in it. Other than that, you find that sweet spot and just leave it there.
Long arc, short arc, heliarc and in-the-dark!