in prime

in one's (or its) prime

Fig. at one's or its peak or best time. Our dog—which is in its prime—is very active. The building was in its prime back in the Fifties, but it has not been well maintained. I could work long hours when I was in my prime.
See also: prime

in your/its prime

in someone's or something's best, most successful, or most productive stage She retired in her prime, but continued working part-time as a consultant. Though the magazine was in its prime, it stopped publication when the chief editor quit.
Usage notes: often used in the form in the prime of (your) life: The members of our squadron were in the prime of life.
See also: prime
References in classic literature ?
The hired men and the teams were in the harvest fields behind the house, and the corn and wheat seemed to the child to be in prime condition.
There is a chance that America's worst comedy nightmare could wind up in prime time next season on Fox, with his own series casting him as the slacker son of a rich business executive.
Photo Pauly Shore could wind up in prime time next season on Fox.
NBC will carry a live game in prime time every Saturday night at 8:00 p.