If one believes that the lake of fire is literal fire, then there are two possible extremes.

1. Either god is able to make at least as good and hot a fire as King Nebuchadnezzar's fiery furnace. If this is true, death would be instantaneous, as it was with the guards who approached to throw in the three Hebrew worthies.

- OR -

2. god will purposely make his fire weak so the wicked will squirm and be tormented for a longer time - gradually like a slow roasted pig.

If you are even able to consider either of these possibilities, your author asserts that you are serving the god of force, not Yahweh, our loving Father.

However, following this line a little further, and still assuming that the fire is literal, a merciful someone would obviously choose instant death over the sadistic, tormented slow roast.

So, if the fire is literal, the answer to "when does it end?" would be "immediately".

BUT, we are told that it is NOT immediate!

Each suffers according to their sins. The most guilty suffers the most. The most innocent suffers the least.

This is what one would expect of a just ruler.

And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works. Revelation 20:12

This isn't binary - a pass/fail, live/die.

For we must all appear before the judgment seat of the Messiah; that every one may receive the things done in his body, according to that he hath done, whether it be good or bad. 2 Corinthians 5:10

The only way justice can be done, is to make the "punishment" fit the crime. The most guilty will "suffer" the longest and hardest.

Accordingly, hell must be variable.