The heyday or peak period when a person, organization, or culture is at its most prosperous or vigorous.
その俳優は全盛期に多くの映画に出演した。
That actor appeared in many films during his heyday.
企業の全盛期は90年代だったと言われている。
It's said that the company's heyday was in the 1990s.
バンドは全盛期に全国ツアーを行った。
The band did a nationwide tour in its heyday.