Do you think Hell is forever?

I personally don't believe in the fire and brimstone hell, that was just something used to scare people in the middle ages but the other day I heard a really interesting theory-Hell is fire and brimstone but it's a place of purification, not punishment so eventually the soul will be clean enough to enter heaven. I'm not sure if I buy this, I just think hell is a nothingness place where you are apart from God and aren't conscious, like the atheists idea of death, and it is everlasting. Whatt do you think?