How does cruise control affect the life of the pads?
It shouldn't unless it's advanced cruise that also slows the car... In which case slowing the car from the rear makes for smoother braking from a passenger comfort perspective as it limits the nose dive effect………….
Well you could be right Al. I just googled VAG ACC rear pad wear and it appears that under very light braking it applies rear bias for the reason that you stated, and uses normal bias for heavier braking……. and pre-sense for those suicidal moments.

Maybe it’s just a VAG thing.
or maybe it’s total horse shite. 
That's bloody dangerous, as the vehicle has no idea what the road conditions are and could easily spin you if you were on an icy patch
A further search reveals that Volvo’s do the same apparently.

Quoted from a Swedish forum :
‘ Volvo Adaptive Cruise and Pilot Assist is very brake happy instead of coasting to slow down, and uses primarily rear brakes.’
I don’t know for certain Mark, I’m only going on what the Indy told me and what I’ve read, so it’s not factual on my part and could be wrong information.