Your father was right on the money. Still is. Regular use of the parking brake – often erroneously referred to as an emergency brake – is a good practice. I do think the advice about taking the pressure off the parking pawl is probably overcautious, unless you live on a steep hill or someplace where your parked car is likely to be creamed by passing traffic. Keeping the parking-brake cable from freezing up from disuse, however, is good advice, even today with four-wheel disc brakes being commonplace. If the cable doesn’t get regular exercise, it’ll freeze, especially the part of it that’s hanging below the chassis and is constantly bathed in muck. Ditto for the self-adjusting system built into the rear backing plate or rear calliper.