What sort of mileage can I expect from the original brake pads? I have to change the rear tire this weekend (11K miles from the OEM Hoop) so I'll have the perfect opportunity to change the pads if they need it. I've never really looked close so I don't know what to expect.

There is no need to remove the wheel for brake pad relacement, you can do this in a few minutes with wheels installed. Wheel removal is only necessary for Brake disc replacement and (without experience on Silver wing) i would bed this is not necessary with 11k miles...
I have 56000km on mine and i think i have the first set installed but have to replace the Brakedisc in the near future...

At 11K you should not be even close to the service limits on rotors.

Service Limits: mm (in)
Front Rotor: 5.0 (0.20)
Rear Rotor: 5.5 (0.22)

The service manual does not list a minimum service limit (I didn't find one) for the brake pads. There is a reference to a wear limit groove for the parking brake pad and it should be replaced if the wear limit groove is not visible. I did not see any such grrove on the front or rear pads.

At 11K you should not even be close to worn out on brakes unless you are one of those who never lets go of the levers.