My 1999 Silverado made it to like 120k on the front pads. I assumed they needed replacement and I bought front replacements from the dealership and O'Reilly's for the rear. My mechanic called me and said he'd already replaced the front, but they looked good still and rears looked nearly new. So I told him to not replace the rears.
I replaced the second set of fronts at around 240k with the premium brakes from Advanced Auto (but didn't like that they dust, unlike the OEM sets). The previous set wore just a tiny bit uneven, onto the side with the squealer tab but they still had some life left. I checked the rears and still looked good, so I kept on trucking. Currently around 260k.
Most of the earlier miles when I bought the truck at 88k were highway miles, but the past 200k have been a mix of city and highway.