Vikingkingq
Adventurer
Well, the Silver Age is where the continuity focus really started, especially as Marvel really emphasized the shared universe thing, so that editorial would keep close track of who was where/when so that Spider-Man or the X-Men weren't in two places at the same time. This was also the time before the sliding timescale when Marvel made more of an effort to have things happen in real time, so that teen characters would graduate high school and go on to college, etc. and referenced current events.Conan has an arc, absolutely. From youthful barbarian to grizzled king, it's part of what has made the character so compelling (combined with, as you said, having room for any number of tales in between).
I think a lot about comics and continuity. It's a medium that wasn't originally intended to have 50-90 years of continuity in storytelling. When you read golden and silver age comics, while you have recurring villains, you don't have necessarily linear tales other than some multi-issue arcs. There'd be callbacks, individual issues were designed to be able to read without context. Now, good luck trying to jump into reading an X-Men issue cold.
This was abandoned sometime in the late 80s/early 90s as editorial wanted to preserve continuity and keep characters at their peak marketable age while throwing top-selling characters into as many books as possible. Ultimately, I think they chose to preserve the wrong things and that Claremont's model where characters would mature organically and had a beginning, middle, and end was the right one - as long as you modified it with the Cimmerian method to keep selling stories stuck in between.