The term 'incredibly long time' can be represented by two crossword solutions: EON (3 letters) and EONS (4 letters). An EON is a very long period of time, usually millions or billions of years. It is the largest division of geological time, and is divided into eras. An EON is typically used to describe the age of the Earth, which is estimated to be around 4.5 billion years old. EONS are also used to describe the age of the universe, which is estimated to be around 13.8 billion years old. EONS are much longer than eras, epochs, and periods, which are all smaller divisions of geological time.