While the giant breeds do grow quickly, the last thing you want to do is encourage "growing like a weed." In fact, feeding a correct diet with properly balanced calcium, phosphorous and protein ratios is essential to controlling growth within the first year to prevent issues like hypertropic osteodystrophy & osteochondrosis dessicans, among other growth-related problems.
As far as longevity, I know a great number of Dane owners who would beg to differ with your assessment of "7-9 years max." While eight years is considered "average," sooooo many of the shortened lifespans & health issues you encounter in the giant breeds (especially Danes) were caused by unscrupulous backyard breeders who just toss any two dogs together to breed so they can make a buck. BYB'ers don't research pedigrees, they don't health test, they certainly don't bother with showing and titling their dogs, and they don't care about quality. As a result, they pump out sub-standard dogs who often have myriad heath issues (in a breed that due to its sheer size is already prone to them), and ultimately it's the dogs (and the people who love them) that suffer in the end.
You'd probably find it surprising to see how many "double digit" Danes (and other giants) are out there, especially now that so many more - and better - resources are available to help properly meet the needs of these dogs.
LOL, you're not kidding! If I had a dollar for every time I've already heard that (and our pup isn't even home yet), I could more than cover the cost of his future gastropexy.![]()
K~