This is the opportunity 'of a lifetime'. = This sort of opportunity comes along 'once in a lifetime'. [=this is a very rare opportunity]
a baseball player's 'lifetime' batting average [=batting average measured over a baseball player's full career]
She was presented with a 'lifetime' achievement award. [=an award for all the work she has done in her life]
(..) I told you already, this is... Wait. What sorcery is this? Some people wait a lifetime For a moment like this Some people wait a lifetime For a moment like this Whoa, I can't believe it's happening to me Some people wait a lifetime For a moment like this I can't believe it's happening to me I did it! I just jerked it completely off! (..)2012 The Dictator