Look at it this way... Top charging is like cleaning up the tile on the sink at home. Wipe it down with Dawn dish soap, with a sponge, and then rinse with clear water, and sponge dry.
However, sometimes you need to do a thorough scrubbing, so you break out the Bon Ami and the brillo pad, and you need to lean on it a bit with something only very slightly abrasive or polish like, to really get it deep cleaned. That's what an Equalization charge is, going up to 16.0V. You need to put the pressure on, use some heavy duty elbow grease, to really deep clean those lead plate cells and get as much sulfur off of them and back in electrolyte solution as possible.
How often do we deep clean? Only when observation proves it necessary for proper functioning of our batteries. Depends on usage, how deep you discharge, and how good a job you do on getting at or close to a top charge, daily. YMMV.
