Rotating chains give more runtime and less wear on the stuff.
One bar, 5, 8 or 10 chains (depending on your bar, chain and skills), one rim and off you go. Wear them evenly and rotate the chains so they run the same amount of time, take care of the bar and run.
Solid bars with more surface for tiestrap will allow more runtime/chains.
Excessive wear on tiestraps, bar rails from low rakers (to compensate sharpness) ruin the rim. New chain in and rim ruin it fast as it wears in together.
Wearing leave traces that you can see how it was used and help you understand.
I call it chain diagnostic's. Fun and educating just as filing.
You don't change one sprocket on a motorcycle either...