I think it is a kind of slang mostly spoken between young generation(aged 10's-30's). If a result of something is really nice, we say 인생 000, for example 인생 샷(selfie), 인생 사진(photo), 인생 커피(coffee), you can add 인생 on almost every noun. It means that my best thing ever I have made, or got.

인생작품 is a shortened form of 인생 대표 작품. It means "the most excellent work throughout one's life" It can be used for the work(drama/movie/song/music/picture) of artists, actors, musicians or directors.