Not been my experience. Whip the drums off at every service - so just once a year - remove the dust and make sure everything is working right, which it usually is, and "Bob's you auntie"! Rear discs corrode because they rarely do much work and modern "open" road wheel designs let the rain and salt and general road dirt get at them. Also, once they are a few years old, the hand brake mechanisms start to be afflicted with seizure. I've had a lot of trouble over the years with VAG rear calipers with this problem. Also absolutely hate disc calipers with motorized hand brake actuators. Mind you the older type with electric motor driven cables are even worse and often terribly expensive to sort. One of the nice things about the Scala is that, although it has rear discs, at least it has a conventional manual handbrake lever between the seats. So, personally, I'm very happy to have to sort out the occasional problem with a drum rear brake.