The rear pads for the larger rotors (should be 272mm) is 5K0-698-451-A.
Normally the OEMs last a pretty long time, I have many customers with excess of 200k miles on the original rear pads. But some only get about 80 to 100k out of them. The 5 cyl/ automatic will generally be harder on them than other engine/trans combos.
Bosch is likely what is on there from the factory (they'll say Bosch clearly on them), but Textar, Ate, Pagid, Jurid, TRW, are all OEM brands. Plus, even the pad set from the dealer today may not be the same brand as what is on the car. They are all used interchangeably. Also know that Bosch's parts replacement line of pads will NOT be the same as the OEM Bosch ones.
A5 wagons normally get the larger rear brakes, like A5 GTIs and GLIs. The regular A5 sedan got smaller ones, not sure what the NCS cars got off the top of my head.