In The Name of Allaah, The Most Merciful The Bestower of Mercy.
Imaam Muhammad Bin Saaleh Al-Uthaymeen was asked about the saying: “May Allaah prolong your stay (in this life) or may Allaah prolong your life”.
He (rahimahullaah) answered: It is not permissible to utter speech concerning prolongation of one’s stay in this life because a prolongation of one’s life can either be upon good or evil. Indeed, the most evil of people are those whose lives are prolonged whilst their actions are evil. So with regards to this affair, if one were to say: “May Allaah prolong your stay (in this life) upon obedience to him’’, then there is no harm in this speech. [Source: Al-Manaahiy Al-Lafdhiyyah: page: 25]