I'm not talking about the brush-out-the-vent-hose kind of clean. We needed the pull-everything-from-the-wall-vent kind of clean. We were fairly certain it hadn't been done in years and years and years.
I called a local dryer vent cleaning specialist (Superior Dryer Vent Cleaning, for those in the Collin County region). Technician David showed up this past weekend and 30 minutes later had our vent completely cleaned out.
The dryer is working wonderfully well now, which makes me wonder why we waited so many years to get it done. I'm now of the opinion that dryer vent cleaning will be on the first-to-do task list the next time we purchase a home, be it for our residence or as a rental unit. It's just amazing the difference it makes - not to mention how much it reduces the change of a house fire.