This seems to be a complicated question. You may ask what is eternity ? Eternity is time without end or forever or everlasting. The fact is we do not even know today or tomorrow, why bother about eternity ? Human life as we know it is not promised to us too, we may be here now and gone tomorrow. Now if we are not here tomorrow , where will we be ?Either we will exist somewhere or we will not exist anymore. We can take a chance or at least try something.
Everyone has his or her own theory. So who is correct ? In case you are still searching, have you tried the Holy Bible ? If you have yours but still have not read the Bible, then why not try the Bible ?
Personally i started reading the Bible in 1976 and kept reading it up to now 2017 and still going. I have grown a lot through this book. I learned about Jesus and many more.
In 1982 i surrendered my life to Jesus Christ and He became my Lord and Savior. At that time i am ready to face eternity. I will never let go of my Lord Jesus Christ and i pray that He will keep me forever just as He promised in the Bible.