I might think twice about doing a board that was fragile with age, but
otherwise, change 'em all. Like replacing both headlight bulbs if one
goes out--it's just a matter of time before the other one goes.
Do you seriously replace both headlight bulbs when one fails? I know of
nobody who does that. Generally you carry a spare bulb kit and a screwdriver
and if a bulb fails, pull over and change it.
Why not change all other bulbs on the car at the same time? Or change them
all once a year as part of the service [1]? What about bulbs in your house?
[1] OK, this is done for things like lighthouse bulbs which are replaced after so
many hours of operation, but that is a rather different case.
-tony