Continued - decided to desulfate - a pain because you have to disconnect the battery from the car but hey. So get this. Battery disconnected from car -- pre-desulfate: SoH 93% SoC 98% R 3.14/"Good Battery"; post-desulfate: SoH 91% SoC 98% R 3.20/"Good Battery". Connect battery to car (but do not start), check some things then test: SoH 76%/SoC 98%/ R 3.81/"Replace". As I type this I have the car running another charge run with the Romondes but it would seem I'm on track for kaput-or-press-your-luck at 3 years next November. My takeaway for now is that quarterly or semiannual desulfation after a new battery is installed may be wise. Because of the IBS cabling sensitivity and varied whatnot in the way of the B+ cable disconnect, I probably wouldn't do it more than semiannually. But for my next battery, that's the plan in my head. Once SoH goes down it doesn't tend to climb up much, so I don't see the current battery ever getting out of the 70s.

So I have an update for you. I installed the current battery in Nov 2022. Did some top-offs in 2023 but otherwise slacked off, I think the last "no particular reason" charge was late 2023 or Q1 2024. I also decided to just go ahead and let the car do its auto stop/start thing rather than trying to "tune" how/when I used it. So - Nov 2024 I noticed the car was getting pickier about the stop/start, unexpectedly disabling it. First [obvious] sign on an F series MINI that the battery is ticking down. That's about 2 years in the car. I check the charge level using BimmerLink and it's at 83%. Acceptable but on the low side for sure. Low 80s is NOT good -- I remember that much from the prior battery. So I check the SoH using the Romondes, battery still connected to car. It's in the low 70% range and a resistance showing of 4.13 (IIRC) or thereabouts. That's higher than prior (2.97 at pre-install, 3.x post-install various times).

I figured I freaked out over nothing. My Batt. is now 3 years old & Romondes charges to 95% instead of 100%. I charged on mo.ly basis & had to relax my demands. I think that was a major factor. 3 years is all they guarantee so....anything over that is gravy. My Romondes, when I started monthly program did it FAST for long time, then took awhile to come up to 100%, that's when I started thinking HUH ? Then hitting 3 years, I relaxed, so let's play it out & see.

Sorry for the slow reply here, visitor messages work weird, I'm only just now seeing your Oct 22 2024 answer.

I don't know the "right" answer for charging. Charging itself contributes to sulfation; fast charging does so more so than slow/trickle; the alternator is obviously always charging the battery; so the "right" answer is almost certainly as much charging technique and specific-circumstances-of-your-driving as timing. Throw in letting it get low = needs more charging and it's a pretty complicated stew.

I don't know the "right" answer for desulfation. I have been reticent to desulfate post-install because of the whole business of disconnecting the battery altogether from the car, but I may do it in the near future (battery is coming up on 2 years from install). I probably should have done it at Year 1 and then annually, but that's a wild guess and a gut feeling (desulfation only helps so much once the battery has gone so far) -- so my take could 100% be wrong or irrelevant.

is it on a monthly basis ?

I desulfated the batt. as soon as I got the Romondes, I don't recall the results. One thing I see as important to know is How Often Do You Charge Your Batt. ?

Not sure there is a way to get further than 3 years -- but the fact that you did nothing with the battery for the first 15 months (no shade, just noting the math means that's the first year and 3 months -- more than 1/3 the battery life, and at the very beginning) probably has impact here.

Have you tried a desulfate on the battery (you have to disconnect it completely from the car to do that safely and properly) and if so what were the results?