I personally think it's something we learn through trial and error.
I used to update every week and then when I switched from student to working life I changed my schedule to be every two weeks because I knew it wasn't going to be sustainable.
But I think it's important to continue to nurture other ideas while you're working on one project long term. So that you don't burn yourself out creatively.
In my case, I know that until Nitro's world ends I'll only be releasing one-shots (around 24 pages) that I know I can work on alongside and then release in one go.
But when I was a teenager I had many projects I gave up on because I was so excited and then didn't realize I lacked : 1) the skills to make it 2) the foresight to know how motivated I'd be long term.
So now when a new idea pops in my head, I write it down and wait to see if it sticks. If it's something I think about consistently, it goes on the pile of projects I'll be developing in the shadows.
There are also projects I shelved for years and then finished later.
(If you want to see paradise, is one of them)
The only difference is, I didn't share it before I know I'd 100% be finishing it.
I get the frustration as a reader, but I'm just trying to highlight that comics are a huge commitment and most of us won't know if we're ready to see them to the end. Until we've failed a few times.
So while I completely understand why you're annoyed, maybe try to see it as a chance to see projects you'd otherwise never get to read.
I think it's quite special to be allowed to follow someone's passion for a story, even if it means you see it wane over time.