Hurmm, right now I have a couple of stories, one that I already started posting, another that I started writing but still in the process of shaping it up.
For the story I'm already posting (on another website, Sci-fi/Adventure), I reckon I can keep with it for the near year. Not sure exactly how long it will end up being, but considering my characters goal and how things are going? I reckon it will reach between 70k to 90k. Mostly depends on a few ideas I have that I need to determine if I want to expand further upon or not.
The story I have is still a WIP (Fantasy/Adventure/Comedy), I want my main characters to explore the world I built, as the story also explores them, and have key locations in each country visited. But due to the story's nature, it will be shorter chapters (Leaning more towards a Light-novel format for this), so I'm not entirely certain about the length, but I do want to work on it for several years. Its probably my biggest passion project right now.
That's about the best estimates I can give. I never really plan that much about exactly how long I want my stories to be, just that I have the story in mind and want to put it on paper. And I just write it out. Usually end up getting my estimates when I've written my first 10 chapters or so? Around then.