I took a look at a group of players (Wayne Gretzky, Mario Lemieux, Jaromir Jagr, Joe Sakic, Steve Yzerman) and how their offensive output progressed as they aged.
The chart has been adjusted for COVID-19 and lockout shortened seasons, but not for injuries, as injuries tend to happen more frequently as aging occurs. Unplayed seasons have been omitted. Ages are from what is reported on Hockey Reference.
To account for different scoring eras, I made their maximum career point total 1 and everything else is indexed between 0 and 1.
Chances are highly likely that they have peaked already. This is why I want them to re-sign at a higher aggregate percentage of cap than they played at during their current contracts. What's on the table is their decline years - which aren't going to be horrible, but they won't be at this level anymore.
And this also says nothing about unquantifiable leadership intangibles that the composite group brought that they don't seem to possess.