Reveal: The numbers in parentheses after the clues tell you which letter to use from that word in the grid: 5AEPOCH use the 1st letter E, 20AINFINITY use N, 35APERPETUITY use T, 40AMILLENNIUM use U, 53AETERNITY use R, 65AYEAR use Y. These letters together spell ENTURY (A long time with no C) = Long time, no see. I know, I know. For you sticklers, the grid is not quite symmetrical- I meant to put YEARS at sixty-six across but forgot and published. Sorry if that messed you up! I'm thinking most people got this from the title and prompt.