The Earth, and this particular universe won't last forever, but in ordinary terms we are biologically immortal. The cells of our bodies have been dividing from other living cells since the beginning of life on Earth. Physically, genetically, we are several billion years old. Our DNA contains 'know how', instinct, that is infinitely more accomplished, experienced, than the memories, facts, conditioned habits etc. we've accumulated since birth.
Every day, researchers learn more about how the brain stores memories. The idea that those memories acquired since birth survive beyond the death of the brain will soon be widely recognized as a religious superstition. Further, those who reflect seriously on this will see that personal memory that lasted forever would become increasingly burdensome, if not a nightmare.
Have Christians, in clinging to the ego, misunderstood the concept of rebirth, of being born again, of being baptized - washed clean? Why do they use the word, 'selfless' in a positive sense and then turn around and want the self to last forever?
When Buddha was asked (probably by a Hindu) about the afterlife, he said, "When a candle is extinguished and then relit, is it the same flame, or a different flame?"