Listen to what I actually say....not to what you think I seem to say.
'Eternal' in Biblical language paints a picture or literally, "Beyond the horizon." This translates better as what we cannot see or cannot know.
Here in modern Western culture, using the modern English definition for 'eternal' it is translated (more or less) as for all time or never ending.
As Jesus lived in Biblical times using Biblical languages, some thought should be given to the type of punishment he mentioned. You insist that Jesus meant for all time, but if we give thought to Biblical meanings, it is quite possible Jesus was saying something more in line with "unimaginable" punishment, a punishment beyond what we are capable of seeing.
You will be correct in saying I am not a Biblical translator by either training or by any stretch of the imagination. I have, however, long been fascinated by word etymology and changes in definitions. Our culture is not Biblical culture, we see through a modern lens--something impossible for them to have done. Therefore, I try to take a peek through their lens. You are welcome to say I perceive blindly. That may well be the case, but I will still find the different roots, etymologies, changing definitions to be fascinating.