Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him) said: “Saying ‘May you live forever’ is a kind of transgression in du’aa’, because living forever is impossible and is contrary to what Allaah says. Allaah says (interpretation of the meaning):
“Whatsoever is on it (the earth) will perish.
“And We granted not to any human being immortality before you (O Muhammad); then if you die, would they live forever?”
From Majmoo’ Fataawa Ibn ‘Uthaymeen (may Allaah have mercy on him), 3/69.