Related Clues:

• Indefinitely long time periods
• It's heard while leaving
• ''See ya!''
• Cheerio
• Really long time
• Bye-bye
• Zillions of years
• Billions of years, geologically
• Long stretches
• "So long!"
• It's said when taking off
• 'See you later!'
• Ciao cousin
• Forever, figuratively
• "Gotta be going!"