G'day Dave, 
Well as Revelation 20:5 says, "The rest of the dead did not come to life until the thousand years were completed"(NASB). So it would appear that at least for some the gift of eternal life is not given until the end of the millenium.
Verse 4 and 6 tell us that there is another ressurection prior to this, during the time of the judging immediately after armageddon, this is called the "first resurrection" and consists of those who in the last days and during the tribulation who did not "worship the beast or receive its mark" and who "came to life and reigned with Christ for the thousand years." I don't know about others, but the phrase "came to life" reads to me that these people are both those who are resurrected and who survive armageddon but are not yet gifted with perfection, eternal life and/or immortality - I think it means that they are given this gift and this is what the phrase means - this matches what Christ said when he told that man, "let the dead bury the dead" in other words those who are not given (unbelievers) or promised the gift are the "dead", does that make sense?
Basically there are three stages, first are those promised the thrones and role of priesthood along with Christ, in Rev 20:4 it says "there were thrones and they sat down on them" now in the NASB the footnotes connect this to Matt 19:28 and the promise to the Apostles that they would "sit down on twelve thrones and judge Israel" and also to Rev 3:21 where he promises, "I will grant to he who overcomes to sit down with me on my throne as I also overcame and sat down with my Father on his throne." After these people there is a resurrection of those who were "beheaded for their testimony of Jesus" prior to and during the tribulation, these two groups are given their reward at the beginning of the 1,000 years. The rest are resurrected "to a resurrection of life or a resurrection of judgement" and those who do not join the Devil at the end of the millenium or who do not "die at the age of 100" for sins (see Isaiah) during the millenium will be given their gift at the end of the millenium.
Now our interpretation of this is that the first ressurection consists of the annointed, those who are sealed in Christ and who become "sharers in the divine nature" and the second ressurection (the dead who come to life at the end of the millenium) are the "great crowd" of "other sheep", many billions who are given perfect eternal life on a perfected earth. Many ridicule this as creating two "classes" but that is not how we see it, it is simply about different rewards, the ones who live eternally on earth will exist in the condition that God originally made us to have, we will probably have close contact with him and his Son just as Adam did before he sinned.
I hope that wasn't too confusing.
Pax
Corvus.
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All the bits are in the right places, it is about 16cm long, about half a foot long and is a little acrobat, it moved it's arms constantly throughout the scan. We could see the heard beating like the clappers (136 bpm)