I finish my large projects completely except for a few rare times when I need to interrupt the process to do a last minute request for a project.
Having said that I usually have 3 projects going at once. One(sometimes more than one) I'm dreaming and planning for by selecting the fabric or drawing out an idea for a project. I have a quilt notebook that I write my plans for each project in and then write notes/details about the project as I do it. That way I don't forget what I planned and I have a record of the details in case I want to make another like it.
Then I have one I'm actively working on and a third one that I'm hand binding in the evening, making a label for it,washing it and then photographing it.
I use the assembly line method when I'm making multiples of one small project such as placemats, makeup bags etc.
I'm also hand piecing hexagon flowers for a GFG that I'm working on. I do these when I'm watching TV or traveling. That's a 2-4 yr project That I'm having fun with. I plan on having it hand quilted when completed.
I think each person works in the way that is most comfortable to them, doing the things they enjoy most.