Climbing Ventoux is a major accomplishment for a tandem team no matter how you slice it. It's hard. Well done.
Which side of Ventoux did you descend? If you came down the twisty side to Bédoin, I can see it would be very hard on brakes. But if you climb that side and descend to Malaucène you don't have to brake all that much. Aerodynamics exerts a heck of a lot of drag at 90 km/hr, especially sitting up, elbows and knees out, and jackets unzipped and flapping. (We are sub-300lb though.) There is some hard braking for the bends and you need to get started on the braking early but if you can tolerate speeds over 75 km/hr you don't need to brake much on the long tangents, and a quick hard pulse to slow down still leaves lots of time to cool the rotor. We came down non-stop, twice (in two different trips),...nothing melted, no need to adjust pads or anything. There are many much harder descents in France. The north side of Port de Balès in the Pyrenees is very demanding.

The descent from Pas du Peyrol that 2frmMi did is a whole 'nuther matter: 2 km of 15% you wish you were dragging a railway tie behind you with a logging chain.