TFA doesn't exactly go into details, but declining cellular repair is mentioned as a part of the process. If cellular/mitochondrial repair were maintained it would address a lot of your issues with longevity. That being said, if our generation (currently in our 30s) were to instantly start living to 150, I think there would not only be huge financial problems but also some pretty complicated psychological onesies well. I don't expect that this is what they mean, but an increase in longevity like that, even over a few generations, is full of disaster if something isn't done about coinciding birth rates.