My understanding of the chemistry in our lead acid batteries is that the sulfur in the acid starts to precipitate out, forming sulfur crystals on the lead plates, whenever the charge drops below 85%.  Also, the sulfur crystals can be broken up and dissolved back into solution by brief high voltage spikes of electricity over time.  This is the process that the battery chargers that have desulfation modes use to "repair" damaged batteries.  I have experience with this with a 2003 Miata that I bought new and still own.  I have always driven this car for pleasure so it has always had extended periods of sitting depending on what has been going on in my life.  After only 2 years of ownership, the original battery would hold a charge for less than a week that was strong enough to start the car.  Back then I bought a desulfating battery charger and put it on the car as a battery float charger.  At the time I lived in the Seattle area.  In 2007 I moved to Tennessee.  I drove the Miata to Tennessee and left it with at my brother's house and flew back to Seattle.  It was a month later when I finally moved the rest of my things to Tennessee and returned to get the Miata.  After sitting a month, that same original battery was still holding a strong charge and started the car right up.  It went from not being able to hold a charge for a week at only 2 years of age to holding a charge for a month at 4 years of age.  I put the car back on the same float charger and continued with life.  In 2015, I became worried about the original battery in the Miata going bad so I replaced it even though it still worked fine.  I was worried that such an old battery might somehow develop a leak and damage the car.  I installed a new battery which has always been kept on that same battery charger.  Here we are in 2021 and the second battery is now 6 years old, going strong and showing no signs of being less than new condition.  So yes, I think that research I did about batteries back in 2005 when I learned about the importance of keeping a battery charged above 85% has some truth to it.

In my experience, the batteries Japanese cars come with are very good.  The original battery in my WRX went at least 10 years.  I'm now on my 2nd or possibly 3rd aftermarket battery in 8 years.  I do drive the car a lot less now, but try to run it out Monday nights when I go to shoot pool, so at least once a week.

Desulfating and keeping the electrolyte topped off are both standard parts of battery maintenance my father-in-law employs.  Makes a huge difference, especially in vehicles that sit. 
 

You can still get all that stuff, you just have to look for it.  Used to be you could get a rebuild kit at the local auto parts store, but not so much anymore.  Now you need a specialty vendor.  This is who I used for the kit to rebuild the alternator on my '89 GT:

https://alternatorstarterrebuildkits.com/

I would have done the starter too, but I opted to go with the later model mini starter instead, and bought a Motorcraft reman one from RockAuto.

Toploader wrote:

I can confirm that the Motorcraft solenoids are all made in China now too. I ordered one from Rock Auto.
I think I have sourced a USA made NOS solenoid, so will see how I go with that.

Yeah, unfortunately a lot of stuff is, but Motorcraft has criteria that must be met so I'd still feel better with Motorcraft branded parts than generic made in China stuff.