DSK writes:

old fashioned
lead-acid batteries are limited only by how they're treated.
Their life is theoretically infinite.

You couldn't be more wrong.

Sure. But if you discharge it 100% and get to use it less
than 200 times, vs discharging it 50% and using it over
2,000 times, what does that do to the energy density
averaged over the life span?

Nothing. Learn what "energy density" means.