Most people like to think of Happily ever after as the end of a story but the best way to end such a long running series is simply to kill off the main character. Archie will not be the first to employ the death of a character. At one point, Batman was killed off to launch a series of Robin based hero comics. Even Sherlock Holmes was killed off.
I believe killing Archie off would be the best way to end the comic book and it's story line. The character has been around for ages and I think killing a character is a very natural way of ending their story, especially when they've been used for such a long period of time.
There are other ways you can stop current production of a comic series without killing the main character. That way, if some time passes and someone wants to create a spin-off series (much like there are many versions of X-Men or Batman comics), it wouldn't seem far-fetched after the main character has been killed off.
Or leave it open for the possibility of misunderstanding. Like how Sherlock Holmes was "killed off" and then it was easy to come back with a beginning of a different book which explained why he wasn't dead.
Cartoons are iconic, this particular character stayed the same age throughout the series and does not have time to die. There is little violence in this series like Batman and Robin so taking out the lead character does not seem natural at all. There are more lessons to be taught and laughs to be brought by this character in future editions, or simply stop the production of Archie and watch the value of the collectibles with Archie’s name increase in value through time.