Teeth Shaving for Invisalign?

I had a consult and was given my treatment plan. My dentist told me that I would need 0.5mm shaved in between 9 teeth. Is this excessive? Can this be evaluated again at the time of when the procedure is to be done? Has anyone else had to have so many teeth shaved? If so how are your teeth now? She mentioned that I may end up with sensitive teeth or could be prone to tooth decay as the enamel will be removed. I'm nervous about having so many teeth shaved if it will cause me more problems.