I find that many of the workbooks I make are one-time analysis of a particular problem, then I never go back to it again. But sometimes I am asked something like: "That set of charts you did last month on churn by device. Can you refresh it for this month?". So I dig back through the files and find the right Tableau file, but then I have to find the data query that generated the data set in the first place so I can update and refresh.
What I think would be great is a way to document the query I used and other notes about the project, so that when I open it back up a month (or a year) later, I don't have to be Sherlock Holmes to find all the parts that went into the analysis. This would be a page that would not be printed by default, but would serve as a way to keep notes on what you did, what your sources were, who you produced it for, etc.