If they can get you to overpay for the year, they get to use your money for that period of time. Do it for enough customers and it adds up. If they refund your money at the end of the year, they still got to use it for that time, and they made money on it.
I agree with everyone else - just pay what you owe each month. During the time of low bills, put some money away for the expensive bills - if paying the expensive bill is a problem of cash flow.
Mike
Go into the world and do well. But more importantly, go into the world and do good.