TRANSLATION

"Lord Krsna exhibits His pastimes of childhood, boyhood and pre-youth. When He reaches pre-youth, He continues to exist eternally to perform His rasa dance and other pastimes.

The comparison made here is very interesting. Krsna does not grow like an ordinary human being, even though He exhibits His pastimes of childhood, boyhood and pre-youth. When He reaches the age of pre-youth, kaisora, He does not grow any older. He simply remains in His kaisora age. He is therefore described in Brahma-samhita (5.33) as nava-yauvana.

advaitam acyutam anadim ananta-rupam
adyam purana-purusam nava-yauvanam ca
vedesu durlabham adurlabham atma-bhaktau
govindam adi-purusam tam aham bhajami

This nava-yauvana, or pre-youth, is the eternal transcendental form of Krsna. Krsna never grows older than nava-yauvana.