"Does supplication avert the written decree concerning death and life? So, does a supplication for a long life change Allah's decree of death at a specific hour, and does a supplication for death change Allah's decree of a long life? "

Praise be to Allah, and prayers and peace be upon the Messenger of Allah, his family, and companions. To proceed:

There are two types of destiny: a conditional destiny that can be altered by supplication and maintaining kinship ties, and a fixed destiny that cannot be changed. The conditional destiny is as if it is decreed for a person to have an increase in their lifespan and provision if they pray or maintain their kinship ties, as mentioned in the words of the Almighty: 'Allah wipes out what He wills and confirms [what He wills]; and with Him is the Mother of the Book.' As for the fixed destiny, it is what is previously known by Allah to occur, and nothing can change it. It is necessary to exercise caution concerning discussions of destiny, as it is a slippery slope and a mislead for understanding.

And Allah knows best.