The phrase, everlasting life, stands in stark contrast to the word for, death, from the previous verse. Both terms stand for equal duration.
Everlasting life, by definition, means eternal life.
And by the same token, death of an equal duration, means eternal death.
Those who obey the terms for life, receive the gift of eternal life.
Those who are disobedient to the terms for life, receive the curse of eternal death.
The terms for life, come by way of faith. The terms for death, reject faith, and depend entirely on the works of the individual.
The works of the individual, are wrapped up in the concept which we call sin. This is mans effort to achieve his own salvation, by means of his own work, presuming that God will accept mans effort.
Salvation by faith, rejects man’s work, and accepts only Gods work.
Therefore, eternal death, which is based on the rejection of faith, results solely from the effort of mans works.
Since Jesus Christ went to the cross and paid the price for all sin, then sin having been paid in full, is not the basis for eternal condemnation. However, mans rejection of faith, means that he is relying on the effort of sin, which is human works, and that becomes the basis of eternal condemnation.
The two contrasting methods for obtaining salvation, are mans works, and Gods works.
Faith relies on Gods work, for which man receives no credit, but is the means of salvation as a gift from God to man, and is received by man by means of faith.
The fruit, or production, as it were, of faith, is eternal life.
The fruit, or the production of the sin nature, as it were, is eternal condemnation.
Just as eternal life is eternal and permanent, and not temporary, so too, eternal condemnation is not temporary, but is permanent.