The title of this question says it all.
Are there nouns for longer periods than a millennium ?
I mean words designating a specific number of years.
Era, age and epoch don't count as they just indicate a period of time (possibly quite long) that is not counted in years, but that is defined by of a characteristic of that period.
(E.g the "Age of the Dinosaurs" was a fair number of millions of years, but not a specific number.)