I think there are a lot of factors.
Ambient temp
How often and deep are the cycles
How many cycles? (20 or 30 in a season or 300 a year?)
Charging voltage
Age of batteries
I wasn't aware that one had to charge at greater than 15 volts to get to 100%. My hydrometer would argue with that. The only time I have seen 15 volts or greater is temp compensated in the winter and a couple of times that I tried out the equalization function. I now understand that unless called for by the hydrometer, excessive equalization is harmful for the batteries and can also cause early demise of the batteries.
If you have the time for it, slow and steady gets the job done with less wear and tear on the batteries. But then I don't often go to 50% soc. More like 75 to 85%.
So the answer is: It depends.
