"forever" and "eternal" is conditional?

Question

Exodus 21:6 Then his master shall bring him unto the judges; he shall also bring him to the door, or unto the door post; and his master shall bore his ear through with an aul; and he shall serve him for ever

Jude 1:7 Even as Sodom and Gomorrah, and the cities about them in like manner, giving themselves over to fornication, and going after strange flesh, are set forth for an example, suffering the vengeance of eternal fire.

"aion" also means "eternity"
Mathew 13:39 The enemy that sowed them is the devil; the harvest is the end of the world (aion); and the reapers are the angels.

so eternity is a measure of time?

Answer 1

Eternity isn't conditional. In Exodus, 'forever' means the entirety of his life. In Jude, it's referring to a more spiritual existence. The people of Sodom and Gomorrah are burning forever in Hell for as long as God lives (forever). Matthew, likewise, is referring to the spiritual. The angels' harvest is people; the reward, the rest of our (spiritual) existence with God in Heaven (forever). Thus 'forever' and 'eternity' both mean 'the rest of one's existence.' Physically, this is until death. Spiritually, this is without end.

Answer 2

I suppose the only condition that is placed on it is "where" and with which part of a person, body, soul, Spirit.

Tough questions.
Again I am not a theologist, however, I would hazard a guess that the slave, serving forever means as long as he is alive.

The Sodom and Gomorrah, could actually be both, burned physically, then sent to hell to burn more.