祖母は九十八歳で天寿を全うした。
My grandmother lived out her natural lifespan, passing away at ninety-eight.
病気もせず天寿を迎えられるのは幸せなことだ。
It is a blessing to reach the end of one's natural life without falling ill.
その猫は家族に見守られながら天寿を全うした。
The cat lived out its natural life, watched over by the family.