For the individual believer, their entrance into Eternal Life does, in that same sense, come at their conversion, with their acceptance of their blessed condition within the Family of God & their surrender to their Father's will for their lives! However since the Body in question, according to Scripture, though it included individual human bodies, was & is the Body of Israel, or more to the point, the Body of Christ; we should note that our entrance into Eternal Life began, not at the moment of our individual conversion, but when the Body of Israel became One with the Body of Christ!
Our biological bodies will perish, there should be no question there, but our spirits return to Him who gave it, to Him who is both Eternal & Eternity! When we, that is, our spirit, enters that Eternity, that Eternal Life which is our Creator, through His Son, Jesus the Christ, we enter that which has always been! Eternal Life is just that, eternal; the Life that comes through blessed relationship with our Creator will never cease & though this biology will cease, just as Lazarus undoubtedly died again, our spirit will persevere!
Charles Haddon Shank