For love to be eternal, the Person must be immortal first.
The Bible clearly teaches that God “alone*” has “immortality”:
“Who (God) only is having immortality, dwelling in light unapproachable, whom no one of men did see, nor is able to see, to whom is honour and might age-during! Amen.” (1 Timothy 6:16)
Hence, for eternal love, one must fall in Love with God only which is the Purest form of Love.
*We live because He lives.