https://batteryuniversity.com/learn/article/corrosion_shedding_and_internal_short

But.. you get those fantastic sunrises almost every day, and all that..    

As I'm sure most everyone knows, SLI (starter, lights, ignition) auto batteries are a different animal from golf cart deep cycle batteries. There are lots of compromises: plate thickness vs surface area, lead alloys, sulfuric acid concentration, etc. that trade off between longevity, cranking rates, and cycling ability. 

SLI batteries generally are never expected to cycle at all, 30 seconds cranking a starter at 300 amps is still only a couple of amp hours.  And temp has a huge impact on corrosion lifetime. When I lived in Phoenix I don't think I ever got more than 3-4 years on a SLI battery.

There are high quality telecom UPS lead acid batteries that are still serviceable after 25 years or more, but they are very rarely cycled, aren't expected to produce high currents, and are kept constantly charged in an air conditioned room.

So I should have been more clear: I think 8 years is very very good for golf cart type flooded batteries, which are designed to take lots of cycling and charging abuse at the expense of higher corrosion rates and relatively shorter life spans due to that.

Not to take away David from your 18 year old starter battery, that is really great.

I'd love to have a classic car again but here in the outer banks cars turn into rolling piles of iron oxide in short order. Wouldn't be worth the heartbreak.  And because of the flooding  ground level enclosed garages aren't a great idea.  Better to just leave them outside and let the rain rinse at least some of the salt off, and don't get too attached...

Right behind you MarWayne, our batteries were purchased in February 2011, so the math shows 7.5 years and still going strong.  Just got back from a 3 day stint in Manistique, MI boondocking for 3 days along Lake Michigan, used the furnace a fair amount for 2 nights, three day report still showed 2/3 battery life; I am not complaining.

Furpod,  the Mustang thing has me thinking about a couple of great cars I wish I still had but 1 was "borrowed" and never returned, a '64 Dodge Polara 500 with hemi and then a '69 Corvette convertible with removable hard-top.  That one I had to sell during my junior year at Michigan State as I was putting my way through school and was running out of money.  Sold the Vette with the 2 tops and bought (can you believe?) a brand new AMC Gremlin and was still had $ 1200.00 left in my pocket and the insurance was going to be 75% less as well.  A humbling thing to do but I was able to finish college w/o having to borrow a cent. 

I don't think that was a malfunction.. I think it was user error, looked to me like the T shirt came out just as designed.. ROFL.

Did make me jump a bit when it did..

It's another one of those things.. yes a sitting battery can/will sulfate, BUT will it do it bad enough that A) it won't clear up when the battery is charged hard, and B) how long does it take to really cause damage noticeable to a casual user? Again, while I KNOW there is absolutely "the right way" to care for batteries, the military drilled into me, because my life depended on them working 100% in all conditions.

It turns out for many casual users, "good enough is.. good enough".

Starting battery in our hot rod was put in in 2010. Red Top Auto Zone battery, has been completely flat a few times, car gets about 750 miles a year in a good year, (hasn't been out of the drive this year) Battery still takes and holds a charge fine. It just sat for 8 weeks because of my needing both RV spots open for my parents visit. Put it on a old Craftsman 10/6/2 charger for 12 hours, cranked up just fine, moved 3-4 times since, started every time. I will be more than happy if I get anymore life out of it, let alone another 10 years. Though.. I have started to have pretty serious thoughts of letting the old Mustang go..

I installed a battery cut-off switch (see my mods for pictures since I used a different type from the one used in the pictures I have seen in this topic so far) after the first time I had to take it to the dealer for service and had to undo my first version battery lock-down system (pictures also in my mods) to get to the battery terminal to disconnect it. Version two is easier, but the battery cut-off switch is even easier than that since I don't have to unlock and undo the battery lock-down. I still have to get to the batteries periodically to check electrolyte level and add distilled water if needed.

At home, my RP179 stays plugged in. It used to be with a 15A adapter to an outlet on the house. Recently, I installed a 30A RV outlet so now I can run the AC, refrigerator, and water heater if needed on AC while the 'Pod is parked in my driveway.

I put ours right on the box. I just cut out one of the box vents and mounted it through that hole. I used a HELLA brand switch not a Chinese knock off, 7 years later, the switch still works fine according to the current owners.

I used the same switch when we changed to dual GC2's..