Only one question needs to be answered really, are you using it ? I have one and whilst it truly is amazing, I haven't put it on my camera for 6 months or more. Before that, It was months again.
I'm thinking of selling mine too, I haven't taken 500 shots with it in 2 years probably, it's not a focal length that's useful to me, I bought into the hype. ( justified hype too )