Related Clues:

• Immeasurable period
• Loooong wait
• Laundry detergent brand
• Historic time
• See 30-Across
• Heating choice
• Stat for Clemens
• See 54-Down
• Forever, seemingly
• See 16-Down
• Notable time
• Diamond stat
• Many a moon
• Wax unit?
• Prohibition ___ (1920-33)