So the Long Now Foundation loves eras, tens of thousands of years, and such. I propose another method by which they can encourage people to think in grand terms: a new unit of time.
The Diplomacy would be defined as the mean time it takes to finish one game of Diplomacy. From my experience, this would be roughly 10 hours, after which players tend to leave to get drunk or find out what daylight looks like. Of course, that would be the English, or standard, Diplomacy.
The metric Diplomacy would be roughly infinity, because games are never finished. Ever. They just fade away.