When I first started uploading my first work, it was willy-nilly. The book had already been written and it was just a matter of formatting it for Tapas, so I was uploading several times per week (often several times per day). My novels are illustrated, and for the first part of that first book I would only draw a new image with each major plot change. As the story progressed I started doing an image for each episode, so the schedule slowed down a bit but still had no set dates.
That novel is finished and fully posted. It will now only update occasionally as I add asides, short stories, special features, etc.
With my current story content is posted each Saturday because it just happened to be a Saturday when I uploaded my first finished chapter to Tapas. Also, I work 45 hours/week fixing cars. When I get home from work I do a bit of writing or drawing, depending on what I'm working on. This book is also completely written and is being uploaded on Tapas as formatting is complete, but it is also an illustrated novel with a new image, sometimes two images, for each episode. This work is usually completed by Saturday, so that's when it gets uploaded. Lately I've been kind of cheating though - I've got a buffer of about ten episodes already uploaded, scheduled to go "live" each Saturday, so now I don't have to have the work finished by Saturday. If I finish it Sunday, or even Monday, I can still set it to upload on a Saturday. Just so long as I get at least one a week uploaded I won't fall behind.
For special content (extras, character profiles, etc) I do them Wednesdays. For example If I introduce a new character into the story on a Saturday I will do a character profile for the following Wednesday, then the next regularly scheduled update for the following Saturday.
All of my updates go live at 12:01AM PST (or whatever Tapas' default is). That way it's there as people on the east coast (such as myself, I am in Nova Scotia) wake up and check their phones/email/comics/etc.