I've been hearing about life extension for over 50 years now.

It hasn't happened. I don't think it every will in any significant way - as in "ten or more years of increase in life expectancy".

First, any such technology will only go to the rich. If only 0.01% of humans live longer, it won't affect the average lifespan at all.

Second, and more important, it's probable that the human body doesn't work that way.

The best model seems to be that your body is made up of dozens of critical systems, each of which has a lifespan of around one hundred years, but any one of which failing will kill you. (I wasn't able to find the peer reviewed paper that went through this math, unfortunately.)

We can shore up these critical subsystems - sometimes for your whole life, in the case of diabetes - but fairly soon, one or the other breaks down.

I regret this personally. As a member of society, the last thing we need is more rich, old people, or more people in general.