When I got the battery I did not know I had to have the switch turned on that is located on the side of the battery when charging it so I thought it was charging when it was not. I had it charging (I thought) for over 24 hours with the red light on the charger on but the green light never came on. I figured I was doing it correctly so I used the battery all that day fishing and did the same thing to charge it again (I thought) that night. I used it all the next day and the fishfinder/GPS ran perfectly both days. It was still working well at the end of the second day and I could have used it longer. That night when trying to charge it again I figured out that I needed the swith on the side of the battery to be on and after a few short hours the green light also came on and this time I actually charged the battery. To answer your question "does it really last that long" I have to say YES! What really happened is that I started using it with the charge the battery was shipped with, used it for two days (at least six hours each day), and it was still going strong after the two days of use. I can only guess that if I charged it when I got it I would have been able to use it much longer before it had to be charged. I have Lowrance-4 DSI fishfinder/chartplotter. I hope that helps.