I like that you brought up this topic because it has been on my mind for some time. The thing with posting to an online site like Tapas where, while there are varying qualities of work, it's not exactly a professional space where we as artists/creators have to commit to delivering a work on time or at a certain standard. There's no one way to post.
I am of the belief that while amateur/unpaid creators want their readers to enjoy their work, they shouldn't feel obligated to post in a way that is meant to please their audience. The story is what is it - it's the brainchild of the artist. If my posting schedule is sporadic or non-existent, that's fine, because I am not worried about what the readers think nor am I worried about reader retention. And some people do not work in the same way and have their own systems towards posting their works that suit them better than pushing out one completed work after another.
And sometimes, it just takes that long to finish the next chapter! There's nothing to be done for it, so if in the interim the artist/author wants to post the in-between/WIP, that's up to them. They feel that the reader might want to read/see it, so it gets posted.
In that same vein, people will read what they want. If you want to gather a ton of subscribers and treat your work as seriously as you can in order to better your skills.e.t.c., that's fine so long as it's a personal choice. And so long as you post your works without going against the guidelines of the site, there shouldn't be any reason not to do so.
But that's just my opinion on the matter.
