I have had 4 Delco 12v for over 20 years for about 4-5 years each.
About 2 or 3 years ago I had each of the red/+ cables corroding where they came out of the battery box and made a right angle turn to the charger and electric panel. The gauge of the cables was too small, OK 20 years ago but not today. I believe the size of the wires was changed just after mine was built.
I'm sure that's not a reason for the starter problem I just feel like typing