Related Clues:

• Geological period (Var.)
• Very long interval
• Long while
• Charlize Theron film, '-- Flux'
• Extremely long stretch
• Almost an eternity (Var.)
• Indefinitely long period
• Geologic span
• A billion years, in geology
• "___ Flux"
• A very, very long time (Var.)
• A billion years, to geologists
• Many generations
• Immeasurably long period of time (Var.)
• Umpteen millennia