https://www.modernagespirituality.com/what-is-life-cycle-and-how-to-break-the-life-cycle/

why is it so long? as one approaches or enters middle-age, you have to wonder what the next half will be like. the energy level and anticipation has withered, the body does not bounce back as it did in the earlier days. for a sober view of all the things that go on a great article can be found here. they try to put a positive spin on it, but your penis shrinking and teeth decay seem to kill the upside.

what is one to do to consume the time? work begins to be a bit repetitive and risk become something you tend to avoid, hobbies can sports can fill up some time as can travel, but the truth of the matter is that all that travel becomes more of a hassle then anything.

there is some upside when things are down though, according to this article in scientific america:

According to the study, set to be published in the journal Social Science & Medicine, happiness follows a U-shaped curve: It is highest at the beginning and end of our lives and lowest in-between.

so a future of happiness if you can get over the middle, according to the above, if you are healthy in your 70s happiness hits you as if you are 20. getting through the middle can be hard, in any task. when it is year after year, it will probably be harder. perhaps this is why we are happy later, we got over the hump. like enjoying a weekend after a long hard work at week.