The term 'EXTREMELY LONG TIME' can be described by the crossword solutions EONS (4 letters), EON (3 letters), AEON (4 letters), and AGESANDAGES (11 letters). EONS, EON, and AEON all refer to an immeasurably long period of time, usually referring to a span of millions or billions of years. Agesandages is a more colloquial term for a very long period of time, often used to describe something that has been around for a very long time.