The term 'very long period of time' can be summarized by the word 'AEON', which is a four-letter word. An AEON is an indefinite and very long period of time, often used to refer to a period of time that is so long it cannot be measured. It is often used to describe a period of time that is much longer than a human lifespan. In some religions, an AEON is a period of time that is associated with a particular deity or spiritual force.