Keeping the battery charged is not the only reason to start the car once
a week.

Suppose it means that a car battery won't last long if you keep it
steady at top charge level, instead of decharge it down towards 50%,
....[snip]....
I was told that a car battery wouldn't last long anyway for this
application, so even when my car battery is 6-7 years old, it
wouldnt't last more than a year when trickle charged, while it is far
....[snip]....

I understand that battery electrolyte becomes stratified if the batteries
don't receive the shaking they would normally get through vehicle motion
OR by charging hard enough that the electrolyte "boils" enough to mix
itself up.

I do know that the batteries I've used to power all of my 'shack radios
for the last 25 years do NOT last any longer (as I thought they would)
in a quiet/protective environment than the same batteries I put in my
vehicles!

--Myron.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)