The problem is that I've seen a number of developers fall into the trap of trying to bring older content up to date as they improve their craft. If you can avoid it while you're developing the story, I feel it would be better. If, once you finish the story, you can't stand the earlier content, then work on it. Probably it would be good to hold the upgrades to any time you might be having a bit of writer's block on whatever project you're working on.
That's just what I would do. I'm actually trying to avoid that trap by starting with short stories that I can do in a few months and then let them be (hopefully).
True, but there's a big issue with a large chunks of AVNs: they take a long time to finish.
As a result, since most take a couple of years to finish, techs and renders' quality changes.
The result there, is that a fairly large chunk of the content, maybe very outdated visually and so on, and will detract new players.
Just take some of the best AVNs finished 5 years ago or so, most of them look like shit by today's standards, because the early renders maybe as old as 10 years.
Even the worse of the newest crap released recently, can potentially rival the best games done years ago visually.
While story progression is essential, upgrading the older stuff is also important, or new players will simply not even reach the new up to date content.
It is a bit of a catch22, since redoing older content will inevitably lengthen the final release, potentially ending up in a loop: having to rework content that simply keeps getting older and older, as you need more and more time to redo the older stuff.
There aren't any magic formulae here, but forsaking the older content until the final release, will likely end up with a large chunk of people dropping the game early on due to its visual aspect.
