Or in other words: Figure out how many of your instances are running 24/7 and buy that many reservations. By comitting to a small instance for one year you get

Or in other words: Figure out how many of your instances are running 24/7 and buy that many reservations. By comitting to a small instance for one year you get it for $48/month instead of $72/month. If you commit for 3 years the price drops to $35/month. Not too shabby.