buy whichever give the longest warranty only.

buy the newer batch of battery.

lead acid battery lifespan starts the day the plumblum touches the acid.

Manufacturer lately uses less plumbum to lower down the cost and shorten the lifespan.
Good battery are generally heavier due to higher quantity of plumbum

Engineering 20 years ago is about making things last long.
Engineering this days is about making things last longer than warranty period only.

they count by plate? or thickness/amount of the plumbum.

i remember correctly lead acid battery is around 2v per cell ?
so they are 6 cells inside our car battery.

the thicker the plate they last longer as they wont corrode so fast.
over discharging also will reduce the lifespan of the battery.
i doubt will happen to car battery as it is use to start the car only.
after that alternator will take over.

In industry lead acid battery can have design long design lifespan ( i have seen on paper 10 years but unsure if there anything longer than that)

depends on what damage the old battery have.
either chemical related problem probably the video shown can be use?
if sudden death means open circuit.
that one add water or what also no use.
alot of batttery these days face sudden death issue.
u can start the car 10 mins earlier. the next thing u know u try switch on also cant. the plate already gone case