[kaluvic]

This is a big question that I'm sure has been addressed in depth in the past.
My feeling is that I will not re-bond my thru-hull fittings.
You should not assume that your shaft and engine are isolated from each other just because you have the plastic coupler....there are bonding straps that are often used to bond through this coupler.
Usually one on each side of the coupling and often quite flush, so have a close look.