Related Clues:

• Brit's farewell
• Time pieces
• Extra-long durations
• History stretches
• Units of geologic time
• Ciao
• Lengthy time units
• Adieu, elsewhere
• ''Bye-bye,'' elsewhere
• Parting comment
• Very long times
• Ages on end
• Major stretches
• "Toodle-oo"
• London "Later!"