I believe there is a good reason why the plots of the last three books allow and require their protagonists to preach at length.

She, indeed, makes herself known by the letter; but he, by speaking himself, and saying what the poet, not what the plot requires.

The plot required him to be admired for the virtues of his actions.

A clear-cut plot of land requires about 50 years before it can be cut again.

There are a small number of NPCs as the plot requires.

Also, its plot requires total surrender of disbelief by the audience.

The plot, which spans the years from 1845 to 1911, requires tremendous compression.

He was even more impressive when the plot required Danilo to show his love for the widow and his determination to marry her.

Although a typical plot might easily require a few thousand paper motions, back and forth, the paper doesn't slip.

Many plots required a two-fold saltation load to be considered.