Dean Stockwell, too. First role in 1945, title role in The Boy With Green Hair in '48, last role in 2015.
I thought of him the other day when he featured in a Columbo episode. Well after The Boy With Green Hair and well before Quantum Leap and The Player
An exceptionally long career, and I loved Stockwell’s work, but it was punctuated by long stretches in which he either had stepped away from acting (the late '60s), or was doing guest roles on TV shows (most of the 1970s), so I’m not sure how consistently he met your criteria in your OP of being consistently relevant and visible.
Yeah its probably a personal thing. I wasnt like a huge fan or anything, but i noted him when i saw him.
Just thought of one that, even by the narrow standards I set, beats Devito by a fair hunk
Kurt Russell. Probably came to public eye the earliest with stuff like The Computer Wore Tennis Shoes (Though of course can be seen in fare like Gilligans Island) and is still going strong.
Not the longest, but I was impressed to see Christopher Lloyd in an episode of The Mandalorian last night at age 84. And he got shot and lived.
Also didn’t realize his first movie was One Flew Over the Cukoo’s Nest in 1975. He got a late start.
I was trying to think of child actors who continued into adulthood, and remembered Stockwell.
Ke Huy Quan could be an answer to this thread in 40 years or so, though he probably doesn’t meet the consistently visible part.
I should have thought of him. He kicked Elvis Presley in the shin in It Happened at the World’s Fair in '63, then played Elvis as an adult (twice, if you include voice work).
Helen Mirren, first acting credit I see is 1967 and she’s been in everything from Shakespeare to Fast and Furious movies.
Donald Sutherland (87) probably first rose to relevance in the mid-60s, and has several projects coming out this year.
I know we just lost her, but doesn’t Betty White’s TV/radio/movie career go back to the 1760s? I mean, she entertained the troops at Valley Forge, right? The woman never took a day off. I believe her Lithium batteries just couldn’t hold a charge any longer. What a loss!
Credits going back to 1954, first credited in 1955, and still going!
From one perspective, if actors are still working, they are “relevant.”
Didn’t start as far back as some but I would argue Anthony Hopkins is currently more relevant than many mentioned. His first movie role was a big one in Lion in Winter 1968 acting with O’Toole and Hepburn. In 2021 he was the oldest Oscar nominee and winner for best actor.
Bruce Dern shared the stage with Paul Newman and the screen with John Wayne. Dude was in Tarantino’s Once Upon A Time In Hollywood in 2019. You know how many roles he has had since then? TWENTY! And he’s got three more currently in post-production, and two more filming!!
From Dern’s Wikipedia page:
“If you think I’m gonna retire so Jimmy fucking Caan can get another part from me, you’re dead wrong. Because I’m gonna go till I’m 100. My goal is to do stuff with older characters that people never got the chance to do, because they never lived long enough… And because I don’t have anything else I can do."
Right on, Mr. Dern!
Glad you mentioned him, as he was the first who came to my mind. He may at this point be “retired,” but I’m sure he would gladly step in front of a camera again for the right role.
He had a stretch of bad movies for a while there, so his relevance during that period might be questioned by some, but the fact is, he was still being sought after for starring roles, was still a “name,” and was still making good money at it.
He put on a terrific performance in the movie that just won Best Picture. That’s very relevant indeed.
Removing my entry because I skipped over Dropo, who mentioned him first!
Were we to give points for consistency…though his career is a lot shorter then many mentioned here…Harrison Ford would be right up there.
Harrison Ford’s career goes back to the silents! He was in the 1923 version of Vanity Fair! Oh, wait…
There aren’t many roles for 80+ year old tough guys. 
I was watching an Outer Limits episode recently - the one where the Chinese develop plastic face-changing technology and are trying to infiltrate the US government - and I recognized one of the Chinese agents as James Hong! (I think I even blurted out “Holy crap that’s James Hong!”) That was probably 1964 or 65 ish.