I found website that provides step by step instructions regarding changing rear brake pads on an S80. Surprisingly to me, they did not turn the rotors prior to putting on the new pads. I've always thought turning the rotors was required. Thoughts???

OEM pads are reasonably soft and do not require the rotors to be turned. Unless, of course, the rotors are scarred or warpped. Just remember, the thickness of the rotor needs to be measured. Rule of thumb is to replace the rotor every other set of pads.
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My name is Klaus and I am a Volvoholic.

One of the rotors was kinda ugly, so I had both turned (as long as I was getting one done, why not do both). I was surprised that pads in the rear were completely gone at 87k. I've never done rear brakes on any car - usually they do not wear that much.

Before there was ABS, the rear brakes were "detuned" to be only about 35% of the pressure of the fronts. With ABS, the rear brakes are no longer "detuned" and can apply more pressure without fear of lockup.

Rear pads still last about twice as long as fronts, but need to be checked when the fronts get ready to be replace.
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My name is Klaus and I am a Volvoholic.