The great Baptist preacher, Alexander MacLaren, says that this promise will still be true in heaven. “There,” he says, “each new moment shall bring new strength, and growing millenniums but add fresh vigour to our immortal life.” Quoting Swedenborg, Maclaren says that “the oldest angels look the youngest . . . When life is immortal, the longer it lasts the stronger it becomes.” And so the angels who have stood before God’s throne the longest, look the youngest. 
The key then to growing from strength to strength, the key to gaining youthful strength, is to wait on the Lord. “Even the youths shall faint and be weary, And the young men shall utterly fall, But those who wait on the LORD Shall renew their strength; They shall mount up with wings like eagles, They shall run and not be weary, They shall walk and not faint.But they that wait on the Lord shall renew their strength” (Isa. 40:30-31, NKJV).
That’s why I do believe that when we get to heaven, we will all look young and handsome and beautiful. Do you believe that? You will look young and beautiful in heaven. Because the longer you wait on the Lord, the younger you will look.
“As your days, so shall your strength be.” As long as your days, so shall your strength be. Even after your days on earth, you will find strength in heaven. And as your days in heaven, so shall your strength be. Since your days in heaven are eternal, so shall your strength be also eternal.
 Alexander Maclaren, “Shod for the Road,” http://preceptaustin.org/maclaren_on_deuteronomy.htm (accessed January 8, 2010).