Related Clues:
- Ages and ages and ages
- Extensive period
- Immeasurable time
- Billion-year time period
- One billion years, geologically
- Humongous span
- Extended period?
- Annoying wait, facetiously
- Untold eras
- Inconceivable stretch
- The time it takes mountains to rise
- Ages and ages (Var.)
- Geological period (Var.)
- Very long interval
- Long while