盛年

zhèng dāng shèng nián

正当盛年

in one's prime

tā zài shèng nián shí lí shì

他在盛年时离世。

He died in the prime of his life.

jí bìng jié shù le tā shèng nián de shēng mìng

疾病结束了他盛年的生命。

Disease cut him off in the best part of life.

yí hàn de shì tā yǐ qī shí èr suì le shèng nián bù zài

遗憾的是他已七十二岁了，盛年不再。

The sad truth is that, at 72, he is past his prime.