Is adding magnesium sulfate to an old battery a good idea even if the battery isn't dead?

I've read in several places that an old lead-acid battery can sometimes be rejuvenated by replacing the sulfuric acid with magnesium sulfate dissolved in distilled water and then charging it. Supposedly, this cleans aculated grunge off the plates and often restores the battery to useful service. What I wonder is whether it's a good idea to add some magnesium sulfate to the water one adds to a battery just in the normal course of things just to keep the battery in good shape even if it's not yet exhibiting problems.