Formal, somewhat literary term used in congratulatory contexts, such as celebrating someone's longevity or referring to a venerable age. Not an everyday word for 'age' or 'life'.
We held a party to celebrate my grandfather's long life.
The stories of those who have reached an advanced age are precious.
Compound of 寿 (long life, congratulations) and 齢 (age). The exact historical derivation is uncertain, but the kanji combination conveys the idea of a celebratory or venerable age.