@Archimage There must be! The alternate theory is it's a tiny portal to a parallel universe. In which case, I feel sorry for whoever's over there — "How can this pen be out of ink already? Where's it all going?"
Only once before have I had a pen drain so cleanly like this; usually there's blotchy residue in the barrel, making it difficult to tell whether it's truly run out of ink or just dried up.
@rnv I misplaced this pen for a few months after an office reorg, but it turned up again recently. I’ve been using it for the last week or so, and it finally gave out this morning. I would therefore estimate that the tip held enough ink for about two weeks of intermittent/moderate use (or two or three days of heavy use) after the barrel appeared empty.
(For those of you who cannot contain your exuberant apophenia, the pen died writing the word who. There is, so far as I can discern, nothing particularly oracular about this, but perhaps the symbolism is lost on me. I am open to interpretations.)