It does seem, from the article, that you don't need to run it too long at higher power settings to gain the benefit. I think Mr. D'Antonio said 15 minutes for every 4 hours of operation. He said to run it at 75% power setting during this 15 minutes.
That wouldn't be my take-away from what the author said. At that point, he was talking about power boats that can plane, being operated in an underloaded condition. An example would be a 27ft. Ranger Tug that can plane it's semi-displacement hull with it's 220 horse Volvo diesel, but the operator wants to save fuel by going 7 knots and running with the throttle barely open. If your vessel is grossly overpowered for slow speeds, then at a minimum, you should get her up on plane and put a load on it for a portion of your time.
A 30 foot sailboat with a 20 horse diesel is something else, entirely. If the diesel can provide 6.8 knots at 75% throttle, but the owner wants to save fuel by running at 50% throttle for 5.2 knots, that's an underloaded situation and is easily avoided entirely by just going 1.6 knots faster (75% throttle), and still burning very little fuel.
I keep my Universal M-25xp diesel at about 75% of peak rpm whenever possible. The only exceptions are no wake zones, operating in the marina, etc.. My engine peaks at 3100 rpm, so 75% throttle is just shy of 2400 rpm, so that's about where I keep her whenever possible.
Main take-way from the article? Run that sucker. It's good for it.