When I was a freshman in college, I took a "world history" class (actually, it was a history of the "20th century world"), and when the professor talked about Winston Churchill's disastrous Gallipoli Campaign--in which the British army, during WWI, tried to take control of the Dardenelles from the Ottoman Empire--I chimed in that I had read something, somewhere, to the effect that later evidence showed that if Churchill had held out for a few more days, the Turks would've surrendered. That professor chided me for what he called the "five more minutes syndrome," the notion that a failed policy will work if only it's given more time.
Well, I don't know if it's a failed project, but I just finished the rough draft of a chapter for my dissertation (it's rough indeed: it has no conclusion and is still 95 pages), and it took at least two weeks longer than I had anticipated. One reason was that I stumbled upon an interesting tidbit in the local papers that cover one of my case studies, and I took a 1 to 2 weed digression in researching the item. It was a true case of serendipity, and actually helped make whatever point it is I'm trying to make in my chapter (I'm not sure what that is.....when it comes to this project, I'm working rather inductively and am trying to draw conclusions as I go). Anyway, I might have spent even more time researching this tangent that turned out not to be a tangent but integral to what I wanted to do.
In my case, the "five more minutes" plea played out.