There absolutely is a finish line: as in, launch the product. In fact, there are countless finish lines in business and product development. You're constantly

There absolutely is a finish line: as in, launch the product. In fact, there are countless finish lines in business and product development. You're constantly running a new race every development cycle. Trends change, competitors change, the entire landscape can change. Sometimes you're going to find yourself flat footed, and you're going to have to start a whole new race to launch a radically altered product. It'd be like saying there was no finish line for the iPhone version 1. Of course there was, they had to actually ship it. And every product iteration has a new race to run and a finish line to meet to put the product on a shelf somewhere to be purchased. The same is true with iterating software of any sort, whether you're talking a micro level finish line (adding a feature to Gmail or Firefox 10.1), or a macro level finish line (shipping a completely revamped Firefox version or launching a radically new email concept with GMail beta). Getting from point A (inspiration, idea, task) to point Z (task completed) = finish line. Try never having a finish line on any task, product, business, etc, and see what happens.