Related Clues:

• Countless centuries
• Long periods of time
• Awfully long time
• Geologic period
• Unbelievably long time
• Mighty long time: Var.
• It goes on and on
• Geologic time
• Longish time span
• Time immemorial
• L-o-n-g time period
• A really long time
• Long period
• A very long time
• It's a stretch