&gt; For it to be useful as a hard-and-fast deadline<p>I think everyone has a rough idea on their personal upper limit of their productive time (for me it&#x27;s 70). There is no lower limit, just like a project with a deadline might be cancelled at anytime.<p>I do not think baseline <i>homo sapiens</i> have the hardware required to cope with immortality or extended lives (all those memories, lack of the human condition). How bad is time compression experienced at age 7000? A week is a long time to a child, I bet the decades will just fly by. I can imagine the ennui. We would have to evolve into something beyond human to cope with this. It&#x27;s not going to be in my lifetime, so excuse me for being comfortable with my mortality.