in prime

in (one's)/its prime

At the peak of one's or something's skill or physical ability; in one's or something's most successful or productive period. In its prime, the company developed some of the most influential video games of all times. I used to be able to bench press over 250 pounds when I was in my prime.
See also: 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
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.