In this portion we learn the role of the Levites. It says they should work at the Tent of Meeting from the ages of 25 to 50, and then they should work no more.
They are not to provide any services. They are just responsible to do the work in the temple.
What this says to me is that certain people should do certain work. We now call this “one's calling.” Not only do people have a calling, but there is a time for working, and there is a time to no longer work.
Why would G_d make such a rule? Was it to give others a chance to work? Was it because when you are younger than 25 you are more likely to make poor decisions, and after the age of 50 your hands might be shaky and you might break something? Or perhaps you have paid your dues.
In the same way that there is a weekly sabbath, there is the sabbath of one's life.
Studying the Torah was not an avocation then, since it hadn't been written yet. And there were still animal offerings. But I wonder what the ancients would do with their life after 50, as I wonder what I should be doing now that I don't work at a regular job.