If you had a rim brake on your tandem you would find it interesting to feel the rims after varying brake efforts to see how much heating occurs, on our first tandem with a total
weight in the 480 range slowing down from 35mph to zero with ~120' drop over ~1/3 mi the rear rim would be too hot to touch and the front warm. For that reason we speced
a rear disc on the newer tandem. Brake adjusting is a little finicky at times and the pads last ~7-9kmiles or about $0.01/mile but I feel more comfortable with the disk on the rear.
Also don't have to worry about the very occasional wet rim and the rim is not abraded by the brakes, FWIW. Weight penalty is ~8-10 ounces per wheel.