Any time I replace ball joints on one of my 8 vehicles, I replace all of them, plus any bushings, tie rods, idler arms and pitman links, if applicable.
I do the work myself, though, so it’s just the parts expense and I can usually get them as a kit on Ebay or through an internet supplier for much less than a mechanic would charge for the parts.
It’s not much more work to do them all at once, since usually you have to remove one part to change another. I just don’t see the point of putting old wear parts back into service if I have to remove them anyway.
Plus, this way I only have to have the car aligned once.
>> my 8 vehicles
My, what an awesome carbon footprint you have! Does Al Gore know about this? :-)