Every time my daughter came to stay, I sneaked a carrier bag full of her stuff into the boot of the car. In this way it has 'only' taken me eight years to be rid of all of her possessions.
My son has another week at home before he returns to university, and I was looking in despair at all of the text books he still has from school. (We own them, I bought them rather than have him keep on leaving them at school when he needed them for homework, he has a short-term memory problem)
So he is currently upstairs sorting out 6 years' worth of text books ready for Ebaying. It's a start, but we have a whole den full of Lego and filming equipment - his hobby was making animated films entirely of Lego, and also writing the music for them. My husband looks at that room longingly, but as he was the one who encouraged it and bought it all, it's his own fault! That rom also contains musical instruments and recording equipment, DVds and books. I think it's going to take more than eight years to shif that lot - and there's also his bedroom with its hundreds of books, which we would love to be able to use as a spare room at some point.