Most lithium chargers go into sleep mode once the battery is charged so there is not problem with just leaving them plugged in and no timer is needed.  Mine stay plugged in all the time ensuring that I've always got a fully charged battery.  I just tested 3 chargers with fully charged batteries in them by plugging them into my Kill-a-watt  and they are pulling just 2 watts for all 3 chargers which is probably just the circuit for the LED that indicates that they are charged.  The timer probably pull 1 or 2 watts on it is own so it is not saving you much.   

--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.