They grow from childhood to youth most of the gods. Then we will not see many of them reaching their old age and they(like Shani) are said to be alive to this day.
- Do they stop aging at a certain age?
- Do they live forever?
All die in this material world though their life spans may vary.
This talks about residents in some heavenly like planets in Jambudvipa
SB 5.16.25: The residents of the material world who enjoy the products of these flowing rivers have no wrinkles on their bodies and no grey hair. They never feel fatigue, and perspiration does not give their bodies a bad odor. They are not afflicted by old age, disease or untimely death, they do not suffer from chilly cold or scorching heat, nor do their bodies lose their luster. They all live very happily, without anxieties, until death.
If these residents can live without old age, clearly devatas on higher planets don't get old. They die at the fixed timings in their youthful bodies.
SB 3.11.24 — Each and every Manu enjoys a life of a little more than seventy-one sets of four millenniums.
SB 3.11.25 — After the dissolution of each and every Manu, the next Manu comes in order, along with his descendants, who rule over the different planets; but the seven famous sages, and demigods like Indra and their followers, such as the Gandharvas, all appear simultaneously with Manu
SB 3.11.33 — Thus the process of the exhaustion of the duration of life exists for every one of the living beings, including Lord Brahmā. One’s life endures for only one hundred years, in terms of the times in the different planets.
SB 3.11.38 — The duration of the two parts of Brahmā’s life, as above mentioned, is calculated to be equal to one nimeṣa [less than a second] for the Supreme Personality of Godhead, who is unchanging and unlimited and is the cause of all causes of the universe