the chance, etc. of a lifetime

of a lifetime

Used to describe something extremely important, enjoyable, or exceptional, especially that which isn't likely to occur again. They offered me the chance of a lifetime to travel the world and write about my experiences abroad. That tour around Europe really was the trip of a lifetime!
See also: lifetime, of

the chance, etc. of a ˈlifetime

a wonderful opportunity, etc. that you are not likely to get again: This is your chance to win the trip of a lifetime!
See also: lifetime, of