Equalization should be done based on the hydrometer readings of your cells being out of whack. As a scheduled activity most advice I've seen suggests once every six months. These types of routine equalization only last 1-3hrs. Any time you are so severely overvolting the batteries you NEED to be closely monitoring the batteries, especially the temperatures, and MUST suspend charging until they return to normal temperatures, before continuing the equalization. (The equalization process stresses and shortens the lifespan of a battery, just not nearly as much as allowing the sulfide buildup.)
You should never have a battery so badly sulfated that you need to try any equalization over a couple hours. But if someone gave you some (from their neglected system), you could try a long term equalization, monitoring closely and suspending charging as required ( I would rig a thermal shutdown and restart, and do the job outside the house or garage, in a shed.) These "recovered" batteries would have a shortened lifespan as a result of the process, but if you got them for free or cheap enough, it might be worth the trouble.
Luck; Ken