Possible Clues:

• The writer's advisor accepting second idea, initially as a reminder of impermanence
• Reminder that death is inevitable (Latin)
• Reminder of expiry marks no more time to be wasted
• Married: no more time to mess around — here's a reminder!
• Novel by Muriel Spark
• A reminder of death
• A reminder of death's inevitability
• Reminder one must pass in Latin
• Reminder of death (eg, skull) (Lat.)
• Metronome I'm activating - it hints at the passage of time