I've always found the term "dead-line" so morbid, so fixed, so unalterable, so threatening. No wonder it's a modern (rather than early modern) word. Good little historical materialist that I am, I much prefer my lines to be plastic, alive, unfixed.
What exactly is a dead line? Is it a condition of modernity?
According to the OED, the first use of "dead-line" as a kind of boundary (1864) described a circumference of safety drawn around a soldier. Outside the "dead-line," the soldier was liable to be shot.
Deadlines are also the early 20th century term for guide-lines "marked on the bed of a printing press."
In the second decade of the 20th century, "dead-line" came to be associated with the time limit for submitting a piece of writing to a journal or newspaper publication.
This last definition is the one that obtains today. It suggests that if the piece of written work isn't turned in within the given time limit, it will not be given literary "life" in publication, thus it falls outside of the invisible time line, and "dies." Of course we sometimes internalize this and worry that if we miss a deadline, a part of us- like an opportunity at posterity, prolonged literary life - will die too.
But for most academics (fellowship, job and conference deadlines excepted), deadlines are more like guidelines. Nobody wants us to turn in or be held responsible for publishing shoddy work, so we ask for a reasonable amount of extra time to get it right. How much time we request depends on the work we are doing. And, in general, the more prolific and well-known we are, the more that deadline, like gold to airy thinness beat, is stretched out.