I believe that the entire idea of accumulating runway from raising money is mostly a fallacy: VC expect money to be used for finding victory (and a bigger one, while you're at it), not for postponing defeat. All of that nice money is earmarked for doing things that you didn't did before, not for filing existing holes.

Staying within the aviation metaphor you get a longer runway, but also a heavier plane with many more seats. You'll better not have oversold on the capabilities of your engines.