I recycle the major points of my supplementals, but update my essays significantly. I would go back and re-read your answers from last year and see how you feel about them and what you might want to change now - because trust me, there will be things you want to change.
I did this last year and got really good feedback from Tufts during my file review - she told me that she felt my essays had been good the first time, but were stronger and more mature the second time around.