One of Luther’s rules for preaching was don’t preach for too long.

Meisner (1587 – 1626) expands on this:

Conclude your sermon so it is brief, appealing and good,
Long sermons just make people annoyed,
You say it takes skill to preach well
It is also a skill to know when to stop,
The preacher who lacks this key ability,
edifies no one.