How long will kolasin aionion, or age-abiding correction, last? Is this subjective for each person? 
No one knows… No one here can provide anything more than speculation. The best answer: As long as necessary.
There are different theories.
The three main categories you’re likely to come across while studying Christian universalist thoughts on the topic are:
1.) It lasts during the millennium reign and ends after that. Note that this could also fit annihilation (with the hopelessly punished being annihilated after the millennium reign). This theory is flexible as to what counts as the millennium reign. This was once a somewhat popular theory but has been largely abandoned, as far as I can tell, since the early 1800s. (At least among Christian universalists. It may still have some prevalence among Christian annihilationists.)
2.) The most prevalent theory around here (which I agree with) is that the punishment can and will last as long as a person continues impenitently fondling one or more sins, which could be eons of the eons. Almost everyone I know of who holds this theory (myself included) thinks it applies to any rational sinners including rebel angels; but we do have one new member on the board who argues that the baby goats are only rebel angels not any other (especially human) sinner.
This theory could be combined with the first one, depending on how the millennial reign is understood. But in any case Christ reigns in this punitive sense until He has submitted all His enemies to Himself as He Himself submits to the Father, after which He stops reigning in this sense and presents the whole righteous totality to the Father. The eonian zoê never ends, but the eonian kolasis does once Christ leads all sinners to repent and to reconcile with God into righteousness. It takes as long as it takes.
3.) A third theory, as a strong minority on this forum, is that the eonian fire and eonian kolasin is/was actually the destruction of Jerusalem, which already happened in 70 CE, and so is already done: it was the kolasin of that eon, at which time Jesus came in His glory with all his angels or messengers with Him to judge all the nations on His glorious throne, sending the uncharitable people into the eonian fire prepared for the devil and his angels but the charitable people into eonian life. I’ll have to let the proponents of this theory explain how they see this fitting together and why they infer it from the data, whether they think it has thus ended already or not, or how long it may last if it hasn’t ended yet, whether it applies as a warning to anyone beyond the time and place of the fall of Jerusalem, etc.
I’m personally undecided between Option 2 and an Option 4, which is that the LoF inhabitants don’t get out until the last penny is paid (Matt. 5:26) regardess of any contrition/repentance in the meantime. This period of time would vary hugely from person to person, and its curve would be skewed way to the right for the Hitler types. Rev 21:8 seems to teach that the punishment extends beyond the millennium. Does anybody have any thoughts on Option 4 yay or nay?
QFT,
I guess it depends on what you see as the “penny” that needs to be paid. In the context of the parable you’re referencing, the debt owed is for the unforgiving and ungrateful servant to forgive and be grateful for the grace given to himself (by the king in the parable, who had already forgiven him prior to his refusal to forgive his fellow servant.) Since the king has already forgiven that vast debt owed, the only thing left for the unforgiving servant to repay is his own unforgiveness. Since we’re told that Jesus died not for our sins only, but also for the sins of the whole world (1 Jn 2:2), I tend to go with #2, in that the only sins we suffer for are the ones we cling to, refusing to relinquish (such as unforgiveness in this case).
Uhhh… where are you finding this option 4? http://i1098.photobucket.com/albums/g374/Paidion9/Emoticons/hmmm.gif
Yeah, I feel that I’m missing a lot of the thread. Not only am I not seeing an option 4, I’m not even sure what passage we’re discussing. 
Did some posts get dropped?
I introduced Option 4 in my first post. It’s the view that LoF inhabitants must serve their full time in the LoF, and that the amount of time varies from person to person. I should have mentioned that an additional point in its favor (arguably) is that if the LoF is at least in part for purification, then the greater sinners need to stay there longer for their own ultimate good.
It’s also possible that if a LoF inhabitant wishes to repent, then this implies that the purification process is complete. This then takes us back to Option 2.
Thanks. I see it now.
Now all I need to know is what passage we’re discussing. 
I am curious about this third one. This perspective would be from someone who affirms pantelism, would it not?
Hi Zoe… as the resident pantelist I’d say this is reasonably close. 
Davo, do you regard Wikipedia’s version of Pantelism identical to your own?
Identical? hmm, but close. I actually wrote a good portion of that a long time ago after someone else put an entry up and asked me to clarify their entry. But over time others (no idea who) also chipped in with slight misrepresentations which I got sick of correcting because basically anyone can edit anything on wiki. This below is what I originally put up on Wiki…
That said, this could do with tidying up as well.