I find this article interesting https://www.talkingchop.com/2019/2/9/18202695/baseball-analysis-primer-aging "the big finding is that hitters no longer peak, only decline. That doesn’t mean they start declining right away; the decline doesn’t get notable until around age 29. And again, this isn’t some kind of hard-and-fast rule for every hitter, it just describes what happens on average across the whole population." For those concerned about Cruz continuing to produce, this article supports you https://baseballwithr.wordpress.com/2017/05/08/what-age-do-baseball-players-peak/ When you see the peak performance outliers - remember that Cruz really had a very old peak - maybe he can keep it going after all Julio Franco was still playing (not very well) at 48, but he kept it going right up to that magic number. https://www.baseball-reference.com/players/f/francju01.shtml