The point of longevity is that you retain your mental and physical facilities far longer, so it's almost a certainty people would continue working until the las

The point of longevity is that you retain your mental and physical facilities far longer, so it's almost a certainty people would continue working until the last ~20 years of their life, just like now. You'll still only need to save for the last ~20yrs of life, but you'll have a longer time working during which to do so.