Related Clues:

• A billion years, to Hubble
• Coon's age
• Dog's age
• Eternity, seemingly
• Long period of time
• A month of Sundays
• Prolonged period
• L-o-n-g stretch of time
• Looooong time
• Many millennia (Var.)
• Extremely long time period
• Geological era
• Big stretch
• Time without end
• Quite a long stretch