Related Clues:

• Thousands of centuries
• Forever, so to speak
• Gazillions of years
• Very long spans
• Billions and billions of years
• Long periods, geologically
• Long geologic stretches
• Not the first to tone down in many cases
• One gets mad about short measure time after time
• See 19
• Not seldom met with in soft endearments
• Tone down south's lacking much of the time
• Newspaper's one-off round comes many times
• A lot of bag is back-to-front
• Frequently expressed as decimal