A Note on Short Sermons

A short time ago I noted this from the Rule of St Benedict:

Prayer should therefore be short and pure, unless perhaps it is prolonged under the inspiration of divine grace. In community, however, prayer should always be brief.

Why shouldn't sermons, too, be short and pure? John Torley, a priest and mentor, used to say "sermonettes make Christianettes." I agree, but it's not necessarily a sermon's duration, or lack of it, which makes it an "...ette." That has more to do with its source, focus and driving passion, or lack thereof.