This was definitely a thing just back in the 2000s. You had guys like melo, tmac, Paul pierce, wade, Dwight ect all decline in this age range or way before. People always mentioned lebron still being so good when he was 33. At first that seemed like an anomaly. Now, you have guys like curry, kd, kawhi, dame, lebron still(lol) jimmy butler, all still being in their prime at 33+. Is it an advancement in technology and medicine? Something else?
For three straight years Michael Jordan averaged 40+ minutes per game, Kobe did the same and early in his career LeBron did it four years in a row. The last time someone averaged 40+ minutes was 2010/11 when Monta Ellis played 40.3mpg. Part of the advancements of sports medicine is better understanding of the importance of rest on athletes and its long term benefits, which help extend careers.