Hello, you had a birthday so the day you were born still works as your “beginning”, the only way to become eternal is to acquire salvation which means there would be a point in your life when you cannot die and will create power that will enable you to continue living without aging. This also means that you can live over 100 years old completely youthful. So, the only way to tell if you are on your way towards maintaining longevity is to feel and to see flesh becoming ageless. Since this is so hard to believe and unnatural for people, I guess the thing to do is to be granted salvation and watch as it all happens to you. What passage in the Bible explains to us what happens to our body when we acquire eternal life?
Job 33:25
Modern English Version
25 His flesh will be fresher than a child’s;
he will return to the days of his youth;
Job 33:25
Living Bible
25 Then his body will become as healthy as a child’s, firm and youthful again.
Isaiah 65:20
Living Bible
20 No longer will babies die when only a few days old; no longer will men be considered old at 100! Only sinners will die that young!