Vatsas, are you really applying to
12 schools? Maybe I've just been talking to the wrong group of people but that seems excessive. If you think you have enough time to give all 12 schools good attention on the essays etc then more power to you!
But I recently read a post about someone who pretty much did a copy/paste on his essays and realized later that it was a primary reason why he was not accepted in his top choices. He did not specifically address why that school was unique to him, and guess that the rest of his application did not stand out from others. Just my 2 cents.