There are those who believe that pads have a significant 'bedding in' process and therefore, once a pad conforms to the face of a rotor, it either cannot be broken in again or it would take too much pad material to re- bed the pads. I believe that that might have been true about a million years ago when pad material was soft and no rotors or drums were either round or flat (across the contact surface).
But anything made in our lifetime is well machined, quite flat (bearing surface) and there really is no bedding in process anymore. Sure there are a couple of thousandths of an inch that will wear off new pads but that is about it. The pad is flat when new or old, as is the rotor face, again new or old. So there is no downside, IMO, to taking a flat, 1/2 worn out pad and putting it on the other side of a flat rotor. I would just note where the thicker pads are, remove all of them and put the thin pads where the thickest pads used to be.
As a test, swap pads all around between both calipers / rotors on the front of a modern bike and go for a ride; see if you notice any significant decrease in braking ability. Betcha' you do not.
It is usually linked brakes that cause a dramatic difference in the wear of different pads on the same wheel. Swapping the pads around is merely a method to spreading that wear increase across all the pads so that more of the entire brake pad set can be used.
No, there won't be any increase in wear on the rotor. Rotor wear is merely a result of braking use, the thickness or newness of what pad is where won't make any difference in rotor life or behavior. In fact, there is a bit of an advantage to swapping pads before they are shot; if a pad spends all of its life on one face of a rotor, they tend to wear together and form very small grooves. Swapping the pads changes the relative location of these grooves (the signature of the pad actually) so that they will not get as deep. Put another way, it puts the high spots on the pad in contact with the high spots on the new rotor face and tend to cancel them out.
Brian
Interesting idea. I got about 30,000 miles out of my pads. Some were far more worn then others. 6 of the front 8 could have gone another 10,000 or more. What's the down side of swapping them around? Would that cause more wear on the rotor?