Why is it "bad" to wear contact lenses for longer than the prescribed period?

For example, wearing 2-week wear lenses for 2 months. Please don't reply with the answer "because it is bad for your eyes". This is what my optometrist says. I want some real evidence. 20/20 did a study on non-disposable soft lenses and disposable soft lenses years ago and found they are pretty much the same...(Note that I disinfect and clean my lenses daily)