Even if there were no hadiths about Hazrat Mahdi (pbuh), we would still realize that Hazrat Mahdi (pbuh) has come because of the 8 hadiths

Even if there were no hadiths about Hazrat Mahdi (pbuh), we would still realize that Hazrat Mahdi (pbuh) has come because of the 8 hadiths of our Prophet (saas) about the lifespan of the Earth.