Long run?
I believe the answer is:
eon
(Other definitions for eon that I've seen before include "billion years" , "Vast age; eternity" , "Very long age" , "In time, long division" , "Prolonged period" .)
I believe the answer is:
eon
(Other definitions for eon that I've seen before include "billion years" , "Vast age; eternity" , "Very long age" , "In time, long division" , "Prolonged period" .)