Here is what I know and understand from Scripture.
First, I would like to talk about hell a moment. There are 3 different words translated often as "hell" and two distinct words that many just take as synonyms for "hell". Hell is old English, (possibly derived from norse/germanic), and it means abode of the dead or a covering. The 5 terms or words either translated to "hell" or used as synonyms for such are: 1) sheol 2) hades 3) gehenna 4) tartarus 5) lake of fire. "Sheol" means the pit or grave and is synonymous with "Hades": Hades being used in the Septuagint and through the New Testament to mean just that...the grave, (both of them also denote a covering). Job was a righteous man and spoke of going to sheol. There are other examples, but I will leave it at that. "Gehenna", properly = "the valey of the sons of Hinnom" was a place where, for centuries, was used as a place where Isrealites sacrificed their children to the pagan god "Molech" and in Jesus' day was used as a garbage burning dump. Jesus only spoke of Gehenna to Jerusalem Jews, as did James once. In the valley of Hinnom they would try to keep the fires burning, but commonly this was difficult. When Jesus speaks of destruction and Gehenna it is a picture to the Jerusalem Jew of what He refers to in Matthew 25:41 "pyr to aionion" eternal fire. Gehenna was a picture of this eternal fire. This fire is eternal in its work: the judgement everlasting, but does this act of burning go on forever?...of that I am not fully convinced. "Tartarus" is again Greek in origin and implies more of a verb when used only once by Peter and it pertains to a place or state of the deepest gloomy darkness. The reason I believe Peter even uses "Tartarus" once is because it parralelled their own legends of where the Titans were imprisoned. I believe the usage also reenforces the Genesis 6 interpretation of "sons of God" as angles, or the angels who sinned. "Lake of Fire" or properly, "limnen tou pyros kai theiou"= lake of fire and sulfer, used specifically in Revelation, (a book of symbolism), is a place where the beast, false prophet, satan, death, and hades are all thrown into. Now that I got that out of my system, let me please say this: the wicked will be destroyed, there will be weeping and gnashing of teeth on that great and terrible day, and you do not want to be at that judgement. Repent (turn away) from your sinfullness and believe on Jesus Christ, (the only begotten Son of God who paid for your sins on the cross and was raised from the dead), before it is too late and you go down to the pit or Christ returns and judges the living and the dead. Do I think the dead without Christ burn forever? No, I actually don't. Many will disagree and we can hash that out some other place. But as for the dead of the Old Testament: there were many from Adam to Christ who God justified and the Bible calls righteous. How is this so? The Bible also says "there is only one name under heaven by which we must be saved" Acts 4:12. This is Christ Jesus. He is called the "lamb slain from the foundations of the world" Revelation 13:8 and 1 Peter 1:20. Since God "declares the end from the beginning and from ancient times the things not yet done" Isaiah 46:10, then from the creation the salvific work of Christ was ordained: it wasn't an "if, when", it was ordained by God and a present reality. Jesus life and victorious saving death was not plan b, it was ever plan a-z. Jesus' atoning sacrifice paid for the sins of all those who put their faith in God's redemption. In the OT they couldn't fully realize the way in which God would do this, but the OT saints believed God and this was counted to them for righteousness. That righteousness could only come from one source= the lamb slain from the foundation of the world. There is no such thing as Old Testament wrath and New Testament grace. The Bible tells the whole story of God and man: Christ in the OT forshadowed is in the NT revealed and any moment now He will be revealed in all His glory from the skies: coming on the clouds with all power and authority to judge the living and the dead. I urge you to please turn from your sin and believe on Him before its too late. One day the dead without Christ will be raised, judged, and they and their sinful works will be burned up and consumed. I don't believe God to be a sadist, and do not see judgement as being forever in torment, but the judgement is eternal. You can either perish in flame with your works or live eternally with the God who is so loving as to give His only begotten Son to be abused, mocked, rejected, and crucified for those who are his enemies= you and I. Jesus said, "eternal life is to know the Father and the Son" John 17:3. NOTE: The spirits Jesus preached to in prison, before His bodily ressurection, were the same mentioned in 2 Peter 2:4, "the angels who sinned". Reference that with 1 Peter 3:19-20. God bless you.