Years ago on this site there was a discussion on the effective longevity of shooting guards. I did a bunch a research and it showed, unless you were a freak superstar at the position, that almost all SGs games, even All-Star level SGs, fell off a cliff at about 31-32 years old. Now a bunch of that data had data from decades where most players got in the league at 22 years old but also didn't have the advantages of modern medicine, dietitians and training. But still, it was about ten years and as a SG you lost your legs and your shot just was never the same again.
I could easily see that with players coming in younger and better overall modern advances could push that to 12 years, regardless of age. Someone said that overall GMs would prefer younger players. At 30 compared to 22 or 25, sure as long as the talent level is the same. The advantage of a lower salary and being able to have them more years makes a huge difference. But, depending upon the circumstances with the team as a whole, if you are competing for a title, you want the more experienced guy, talent being equal.