Is it necessary to delete a PIT?

In search after section, ELasticsearch said, "When you’re finished, you should delete your PIT".

Is this necessary? Does a PIT get deleted automatically after timeout? Just as "Scroll" does.

It's not easy to find a good time to delete the PIT, as it's difficult to know when the end user finishes his pagination.

As PIT documentation says Point-in-time is automatically closed when its keep_alive has been elapsed. So it works the same way as scroll. You don't need to manually delete it, as long as the last keep_alive value is not super big (how long the PIT still needs to be around).