It may be worth noting that the word for "eternity" in Greek is "aion," which refers to an indefinitely long rather than necessarily infinite period of time. The same goes for the Hebrew word (which I've forgotten). The phrase usually translated "Eternal Punishment" might be more accurately translated "punishment during the next age."
(I don't actually speak Greek or Hebrew, I just know a few words. I do speak Latin, and generally prefer to read my Vulgate on account of the similarities between Greek and Latin grammar allowing it to be a more literal translation. It usually sticks to saying age (saeculum) but does occasionally say eternal (aeternum, in perpetuum). When on my computer I sometimes go with reading Young's Literal Translation, the only verbatim English translation I know of. It never uses the term eternal, only "age" or "age-during.")
It does seem rather clear that there will be punishments in the next age, but whether this is the same as annihilation is less certain. Some places seem to imply that Christians will be punished for our sins then too, even more harshly than non-believers because we cannot claim ignorance as a defense. Of course, those in Christ would only emerge stronger for the ordeal.
I'm reminded of the parable of the vine and branches. While those who do not remain in Christ are described as being gathered up and burned, this is not until after they had withered and died on their own. It seems these flames are not death or punishment, but disposal of the corpses.
(It may also be with noting that earlier in the passage when most translations say that branches that don't bear fruit are "taken away," the word is literally "lifted." That could mean taken away, but more likely means that the farmer provides supports for the branches that are too weak to stand on their own so that they can get enough light and have room to start growing fruit. Those who have not yet born fruit are treated most gently, not tossed aside unless they fully break away from Christ and die on their own.)
The most common new testament word for "hell" is Gehenna, which was Jerusalem's garbage dump where waste was incinerated and buried for worms to eat up the last of the remains. Most references to wicked there specify their carcasses burning as garbage, not being being executed in fire.
I thought I remembered a verse where God said it would never even cross His mind to kill a son in the fires of Gehenna (which would seem to indicate that he would not sin man to gehanna to die, only their remains after death), but checking back it appears more specific, saying He would never consider ordering sons sacrificed to Moloch on altars that once existed in that valley.
On the other hand, the parable of the weeds does not say anything about them dying on their own before being burnt. Additonally it does say not to fear man who can only destroy the body but God who can destroy both body and soul.
