How long can a battery possibly last

Those old S10 and Ranger 4cyl stick shifts are about indestructable.

My sister put 200K miles on her first S10, dad bought it new for her to drive to school.
It was still nice body wise when she gave it to me, but she hit a cut stone about 18" in diameter, and smashed it dead center with the engine cross-member, never scratched the paint, but the tops of both tires were sticking out the front fenderwells.
She said she backed it back down the road to the local fire department, and they used the jaws of life to cut the sway bar to get the rock out.
I bought a front frame section from the wrecking yard and fixed it. I could not keep my wife out of that little gas-sipper. Wife wrecked it one day, not her fault, I just beat it back out and ran it some-more, until the safety inspection was due, it was not worth fixing again, traded it in on a used neon, and got $1400 out of it.

Sisters current S10 has over 350K on it, she runs the crap out of that little truck, it will not die.
I got an 82 Mazda B2000, 247K. Runs like a top but I did have the head rebuilt and put an NOS carb on it. The exhaust was pretty rusted out past the cat (original!) but I was able to replace the empty muffler and seal up the pinholes in the pipe. Its got a wally mart $29 rebuilt econo battery in it and I have to keep the trickle charger on it as I only start it once a month as its non-op'd out here so I can store it "legally". What a joke. If I dont trickle charge it, it has about 15 seconds of crank left in it, but it always starts right up.