All Things Wear
Brother of The Benz, JRB
All mechanical machinery wear evidentually.
In a distributor; the shaft bushing or in a direct drive from the camshaft the support bushing.
Vacuum retard/advance units.
Electronic Components, i.e. solid state devices or points and condensers. Distributor caps and rotors conducting up to 40,000 volts through worn spark plug wires.
There is no set rule of thumb for replacing any one of these items.
My 1987 W124030 with 176K miles still has the original cap and rotor.
BUT, I just last week I was bragging about my original A/C compressor and this week it failed.
Visually inspect these items and replace them where needed, but it isn't neccesary to replace something just for the fun of it for a cap asnd rotor don't come cheap.
Happy Trails Beep Beep from The Spiderman in Houston!!!