I occasionally find corroded terminals on the 9V NiCad batteries, a couple times I had to replace the battery cable.
As for making the assemblies, I just line up all the parts and don them assembly line style. Trim all the leads the same, then do one soldering step, and the next, etc.
Since I have pre-made cable assemblies, the 3V replacements go really quickly, just trim the cap leads, slide the heatshrink on the cable, solder them, and hit them with the heat gun.
The 9V ones take a little more time, but not bad.