I have an ATV that we rely on for plowing snow. This winter the battery refused to hold a charge for more than three days so I replaced it. The old battery sat for a month in sub-freezing weather waiting for the next dump run. I decided that it might be handy to use for electrical testing with my coming build so I charged it up. While it was percolating away, I recalled Cosmo's Youtube video on desulfating his teardrop battery.
I too have a Noco Genius charger with a desulfate setting. Since the charger claims it's a genius what did I have to lose with this old battery? So I let it sit overnight on the desulfate setting.
It's been two months and that battery is still holding at 12.6 volts.
I bought that ATV two years ago and the owner told me he was selling it because he seldom used it. I assume the battery would sit for several weeks or months without being charged and from what I've read, that's partly what causes sulfation.
Our teardrop battery –-which is a standard Group 27 marine–– is set to hit the road on a two or three-week escapade deep into the deserts of the southwest next week. I think its six years old and has generally had a solar panel juicing it up and has never dipped below about 12.3 volts.
For an old lead-acid battery, I think it's in good health but it'll be sorely needed on this trip --so as soon as the clouds part-- I'll put the Genius on it and run it through the desulfation cycle.

I'll report back if I note any performance change.
T