Age vs career minutes debate

One of the new theories that has been making its way into NBA analyst and media reports is the concept that perhaps it is minutes played, and not age, that determines a player's career arc.  This has become relevant because of the generation of superstars that came straight from high school to the league starting with Kevin Garnett in the mid-90s that are now entering their 30s.  As a Garnett fan, I have seen many recent articles taking it as all-but-a given that the minutes are the key, and since Garnett has already logged more minutes than guys like Larry Bird did in his career there are many ready to hand him his watch and cane as he inevitably slows down.

I guess my question is, though...when did it become a fact that minutes, not age, is the key factor?  I internet-searched to see if there was this body of evidence that I was unaware of, but all I could find were articles like this that mention the theory and then began to run with it as potential fact.  As far as I knew, the whole reason that this was a theory to begin with was that the NBA doesn't have much experience with players that entered the league as teenagers...so why is everyone so confidant now that they know that minutes determine career arc better than age?

Because if you look at their careers thus far it has been age, not games played, that has seemed to determine their production arcs.  After all, if it is minutes played that determines your "player age" then preps-to-pros stars should also hit their peak earlier in their careers, right?  Wrong.  A person just naturally hits their physical peak in their mid-to-late 20s, and the prep-to-pros guys have been no exception.  Kobe Bryant had his best statistical year at age 27, just like Kevin Garnett did.  Meanwhile, Tim Duncan (who played four years of college) peaked statistically at ages 25-26.  Michael Jordan, who played two years of college, hit his statistical peak from ages 24 - 27.  David Robinson, who played four years of college and did a two-year military tour before entering the NBA at age 24 still hit his statistical peak at age 28. 

In other words, the prep-to-pros look exactly like their college-going peers in their career arcs up to this point.  So outside of the fact that this new theory sounds kinda cool...why are we so certain that all of a sudden their career arcs are suddenly going to diverge?  Yes, Charles Barkley and Dominique Wilkins had declined and retired before they had played as many minutes as KG...and they were also 37 and 39 years old.  Unless there is something that I have missed, I am going to wait and see before I decide that the Celtics are on the edge of an age cliff with their roster.  Because as I recall, Hakeem Olajuwon peaked and dominated the league in his early 30s...Karl Malone won two MVPs after the age of 33...Kareem Abdul-Jabbar was named MVP and won four rings after the age of 32.  Players these days are actually healthier and playing LONGER than they did in the past, so pardon me if I require a bit more proof than "well, because someone else thought it might maybe work this way" before I believe something to be true.