Related Clues:

• They're shorter than periods
• A looooong time
• Stretches of history
• Almost eternity
• Millennia on end
• Geologic divisions
• Major time periods
• Loooong time
• An extremely long time
• Unimaginably long time
• Long times to wait
• Many many centuries
• Centuries of centuries
• They last a long time
• Time pieces