Agree with the above postings.
Much of it depends also on the team's comfort level and how you brake.
Grabbing 2 handfuls of brake levers at the last second is only reserved for panic stops . . . yes, we've had a couple.
Modulating the brakes on long descents lets the rims cool momentarily. Apply front brake, let go and do rear brake . . .
Have done an 11 mile continuous 7% downgrade with mountain curves with only old Mafac canti brakes back in the very early 80s without issues. However, did stop half-way into the descent as my fingers were starting to cramp from the repepetitive on/off braking. While stopped we checked the rims; they were warm, but quite touchable and not hot. Continued our descent without any problems.
We are a rather light weight team (under 250 lbs) and had been warned by so-called 'tanbdem experts' that we would not be able to descend the mountain without a drum brake.
So much for tandem 'experts'!
Brake systems and pads have improved greatly since then.
Pedal on TWOgether!
Rudy and Kay/zonatandem