People say many things. It is good to question, if questioning leads to deeper understanding - but not if it destroys faith or prevents faith from naturally blossoming.
Yes, God's love really is unconditional and eternal. It is like the sunshine. But to see the sunshine, you have to open your blinds and shutters. If you keep your windows heavily shuttered, the sun may be shining but you won't see it!
What you do in life prepares the way for what you experience in death. The 14th Psalm goes:
"The fool hath said in his heart, There is no God."
"In his heart" is a very important phrase. People often lead their lives as if there were no God. Yet, they think that if there is a God, then in the afterlife, that is when they will meet with Him and perhaps appreciate Him. But it is not like that. If in life, your stone heart and doubting mind created a Godless world for you, then in death, that is what you will experience. God isn't dissing you or being vindictive. You simply never knew Him; and when you're dead is not the best time to make new acquaintance. Strive to know Him in life through a loving heart and good works. Then death will take care of itself.
A mango has a certain taste. You can study the chemical composition of the mango and know exactly what kind of molecules it has, or how many calories it has; but still, you will not know the taste of the mango.
Let the philosophers worry about whether God's love is unconditional and eternal, exactly how much it weighs, and how long it goes on. Your need (as all our need) is to actually taste God's love - at first sampling only a morsel, but gradually allowing your heart to be consumed by it. Then all your questions will be answered.
Perhaps what is troubling you is eternal damnation. After all, if someone is damned for all eternity, then how can God's love be unconditional and eternal? It's a fair question...
Much is resolved if you think of eternal damnation as a state of consciousness. When someone experiences this hell consciousness, it appears to go on forever; there does not seem to be any escape or respite. While they are experiencing it, it truly is eternal damnation. But eventually, the person has suffered enough to expiate their wrong actions; then they move on. Eventually, they do experience God's love. After all, they have an eternity in which to do so!
In the example that you gave, I think there may be a built-in fallacy. It's as though God is saying: "You didn't do such-and-such for me in life; therefore, in death I will refuse to love you." (In other words, conditionality on God's part.)
I would say rather that a lifetime of thinking, saying, and believing that God doesn't exist would be equivalent to keeping all your shutters closed. You have conditioned yourself to believe that God doesn't exist, and in death that conditioning merely continues. God's love is there, but after a lifetime of shutting it out, you don't experience it in death.
In the Gospel of Thomas (from the Gnostic Gospels), Christ says:
"Look to the living one as long as you live, otherwise you might die and then try to see the living one, and you will be unable to see."
This utterance suggests that we should strive to know God and love God while we are still in the body. If we fail to do so, and later suffer in death, this does not point to a flaw in God's unconditional love.
Another way of dealing with the problem of suffering is to consider alternative views (other than the egoistic view) of exactly *who* is suffering. If each human soul is a spark of God through which He experiences what we experience, then there is a sense in which it is God who is suffering in and through us. Suffering can exist, yet there can also be love.
It is horrible to suffer, especially if we feel alone in our suffering. Yet, the existence of suffering - even in hell - does not negate the notion that God's love is eternal and unconditional.
It seems to me that our view is conditional, in the sense that we feel if God loved us, he would give us everything we ask for, including entry into Heaven as an automatic perk. But God might love us unconditionally, and yet recognize that we are still temporal beings living in a dualistic corner of the universe where we are still subject to a system of rewards and punishments which gradually purifies us and teaches us wisdom.
A.M.