Ski, just keep preaching it brother! You're dead on the money, and I have the hardest time explaining this to hunters and getting them to believe it.
I've had the privilege to work with properties large and small. I've had clients with under 100 acres to work with, and then some giant clubs and private properties (14,000 acres being the largest). On the largest properties, have we been able to improve the buck age structure? Yes, dramatically so. But on the size properties most of us have to work with? Not much. I've been able to help average-sized property clients increase the total number of bucks using their place, but like you stated, the age structure pretty much stays the same year after year.
Below are two graphs from my property. The first is the actual buck population, and the second is the buck age structure. In the first graph, it's clear we've been able to produce fairly dramatic changes in buck population over the years through habitat manipulation. Yet the second graph - buck age structure - shows virtually no change over the years. And my place, at just shy of 500-acres, is not a small property.
How big of a property do you need to alter buck age structure? I don't know the answer to that, but it's going to be in the thousands of acres.