Related Clues:
- Given so much time, pig might fly
- Piles up birthdays
- Thousands of centuries
- "... and children of all ___!"
- Forever, so to speak
- Gazillions of years
- With 19-Across, far back
- Mellows, maybe
- Very long spans
- Billions and billions of years
- Improves in the cask
- Gets older iron, and space-ice perhaps?
- Ice and Stone, e.g
- 'Rock of --'
- Long periods, geologically