Back then capacitors were so much better, they will most likely never go! It was only later on when the electrolyte formula was stolen and passed on did the problems of bad caps start to happen as the formula was wrong, important ingredients were missing, so the caps worked but several years later that's when the problems showed up!
Back in the 1980's I don't think i ever changed a cap unless it was on some HT line of 450v or so, It was always something else capacitors going was not heard of really.