How many devs above 40 do you think still do leetcode to keep themselves entertained, especially if their daily work is doing CRUD stuff between corporate meetings?
Also: when we think about whether we've seen a problem or not before (in order to be honest during an interview), presumably this includes all problems we have a significant memory of, not just problems we've seen recently.
Love to know how many do build bridges, repair cars,..., on their spare time for job interviews.
You can study for the interviews you'd like to have, or the ones you'll actually have.