Meaning of ななじゅう in Japanese

彼は七十歳まで生きた。
He lived to be seventy years old.

そんな失敗なんて気にするな。人の噂も七十五日。みんなすぐに忘れるさ。
I wouldn't let a goof-up like that get to you. People have short memories and the one good thing about gossip is that it's short-lived.