Revising old works in an ongoing series and how to go about it

Something I've been pondering for quite some time is the proper etiquette when it comes to revising/rewriting/re-editing older fics. This is especially true in the case of ongoing series. For example, my Antipode fic series was first published in 2012. However, now that time has passed, I've become more aware of flaws in the first and second stories, including plotholes, characterization issues, logic errors, pacing concerns...

Basically, I want to go back and polish some of the weaker scenes, but I don't want to make things a chore for longtime readers. My plan is to restrict how extreme the edits can be so that I don't do anything that drastically retcons major plot points, but allow myself to address critique I've received in the past.

But I'm curious if any of you have gone back and modified older works in a series, and if so, how you handled the process. Likewise, I'm curious how you would feel as readers if an author went back and edited a story you'd read before. Is there certain etiquette to keep in mind? Any examples of fics that went back and spruced stuff up?

I want to avoid a full rewrite, and I want to avoid making readers feel as though they -need- to read the new versions, but I can't help but wonder if a "Revised on -date here-" note should be added when I'm done.

If your revisions go beyond cleaning up the grammar and spelling, I'd recommend keeping a copy of your original version for the public to read. (Say, copy the old version on Google Docs, and link to it from wherever the main fic is.) You never know, but some readers might decide they like the original better, for whatever reason, and get disappointed if that version disappears forever. Or there might be obsessive completionists, or people who just want to see your evolution as a writer.

The latter actually happened to me. I wrote a novella-length fanfic and unintentionally took a two-year hiatus midway through. When I finished the story, I also went back and extensively edited my already-published chapters, to bring them up to my current standards. I kept copies of the old versions of those chapters, and one of my readers made a point of reading those old versions before he read the final revision.

That's a really good point, actually. :|a Luckily, I'm pretty sure I have all the old drafts saved on my external. Would you recommend Google Docs over something like a blog? Not like tumblr, but something like Dreamwidth, maybe. It's where I store all my drafts.