Usually I go through 2-3 sets of front pads before I have to touch the rears. My Acura at 133K miles, the fronts finally wore down to the squeaker, but the rears were still about 50%. I did replace the whole set just because I had gotten 133K out of them honestly. had it been 50K or so, I would have just done the fronts. But I figured I'd gotten my money's worth lol.
And to the guy that had his calipers replaced, you got ripped off too. You NEVER replace calipers unless they are damaged. If one is wearing uneven, you simply clean the slides and re-grease them, check for any burrs and polish those off, and slap them mo-fo's back on. Calipers only need to be replaced if the seals begin to leak and a new piston/seal wont fix it (possibly a score in the cylinder bore), or if they become physically damaged in some way from a wreck or offroading damage.
Really amazes me to hear what people pay to have done to their cars, when alot of this stuff is basic maintenance items. I can see having a tranny fixed at a shop, or internal engine work, or electrical diagnosis. But brakes? Anyone with a vehicle should know how to rotate tires, service the brakes, replace belts, hoses, and filters, change oil, and replace spark plugs/wires/cap/rotor. This generation of people my age (29) and younger, and some older, are a generation of "Pay to have it done" and either can't or won't learn how to do it themselves. It's great for me as a mechanic, I make tons of money off folks that need simple shit done that they could do in ten minutes themselves. But still, sad at the same time, knowing they could save alot of money if they just took the time to learn. Just an odd world it's becoming it seems when it comes to mechanical knowledge....
