Do you drink too much coffee if you use two tablespoons of grounds to make a 12-cup pot then drink the pot over 10 hours?

If you are using two tablespoons per cup and drinking 12 cups, then yes this is excessive. If you are using two tablespoons for the entire pot then you are okay. No, in effect you are drinking coffee flavored hot water and if that is OK with you then you go right ahead. The measurements you are currently using would make a single (8 oz.) cup for most people.