In talking about Acts 24:15, the WTS says this: "The resurrection of the dead to an opportunity of perfect life on earth will be a supreme act of mercy. Then each one will be able to show appreciation for the gift of true life." Thus when people are resurrected to life on earth, they are only given "an opportunity of perfect life on earth"...be able to show appreciation for the gift of true life." That is those resurrected will not yet be "perfect" but will still have to prove to the WTS god that they are worthy of that god making their life permanent, having their name written in ink, as they are only penciled in so far. The WTS used to use Isaiah 65:20 to back this up saying that someone could still die even at 100 years old. But I cannot even find Isaiah 65:20 discussed in the Watchtower Online. (Not even mentioned in the indexes or in an article, it starts with verse 21. If you can find it let me know. But here is another direction the WTS takes. "In view of that, the “righteous” ones just as well as the “unrighteous” will need more than just liberation from the memorial tombs by resurrection from the dead. The “righteous” will also need liberation from sinfulness and human imperfection. Consequently, the heavenly Judge Jesus Christ cannot pronounce them at once actually innocent, perfect, free from condemnable sinfulness and on their very day of resurrection hand down the decision that they are fit for eternal life on earth. They will mercifully be given the benefits of Christ’s atonement sacrifice so that they can come to human perfection, spiritually and physically. If they are obedient they will not die again. That is why the resurrection of the Judgment Day is called “a better resurrection” than that experienced by those resurrected in Bible days.—Heb. 11:35."
So this is how the WTS puts it. They teach that even some who reach the end of the 1,000 year reign could be executed and go to eternal death. That will be another post.