Also, according to the Making of ROTJ book, the main reason for him wanting to be killed off was the character arc in that particular film. It was not satisfying for him (or the character) and instead of going through the motions of what he was given to work with, he thought it would be better to just kill him off. I know Carrie Fisher also expressed her disdain for Leia's character arc in ROTJ. I have a feeling that is why we heard rumors of Ford saying that he wanted to see Han's character arc throughout the entire trilogy before committing to anything. He did not want a repeat of ROTJ.