Maybe we kept our Fisher Price Baby Monitor plugged in too much, but now we have to.  After using it for about 7 months, we could no longer take the monitor away from the plug, as the receiver battery wouldn't last.  We were very disappointed.  We really do like the lights and sound feature,as that is useful when you have a hair dryer on or something else that you are doing and can't actually hear the monitor.  We also like the dual receiver, so that we can leave one downstairs (the baby's room is upstairs) and one upstairs for when I am in the shower or something like that.