I'm pretty sure this is a foregone conclusion. There's simply no way around the math other than increasing the retirement age. If you go back 50 or 100 years, people didn't sit around for 20 or 30 years after retiring doing nothing - they simply died earlier. So if you're going to live until 80 or 90, you'd better work until at least 75.
If you go back 50 or 100 years, productivity-per-hour was a tiny fraction of what it is today. Why do we decree by fiat that everyone has a moral obligation which we will enforce via the economic system to spend at least half their waking hours working for most of their lifespan?
If you're going to finance your own retirement, feel free to stop working whenever you have enough money saved up. However, if you're going to demand that future generations of workers finance your retirement through taxation (which is how the U.S. Social Security system works), then what you're saying is that future generations have a "moral obligation" to spend ever-increasing fractions of their salaries to fund prior generations as life expectancy increases. Keeping the retirement age the same while life expectancy goes up results in an increasing transfer of wealth from younger generations to older generations, with older people having an increased standard of living at the expense of younger ones.
By the way, higher productivity per hour doesn't necessarily mean that people can afford to pay higher taxes to fund your longer retirement. In many cases, it means that employees are expected to work more hours (e.g., work 50 hours a week and answer e-mails from home) for the same salary. Also, productivity per hour is only likely to have increased in jobs that are based on technology. It's not likely that the productivity per hour of a mail carrier or a teacher or a waiter is much higher than it was decades ago.
If you go back a 100 years, people shat in outhouses and died of TB. Only the rich retired.
Why do we decree by fiat that everyone has a moral obligation which we will enforce via the economic system to spend at least half their waking hours working for most of their lifespan?
If you go back 50 or 100 years, productivity-per-hour was a tiny fraction of what it is today. Why do we decree by fiat that everyone has a moral obligation which we will enforce via the economic system to spend at least half their waking hours working for most of their lifespan?