Review on Maximize Your IRobot'S Efficiency With SPARKOLE'S 5300MAh Extended Life Lithium Ion Battery For Roomba 500-800 Series by Darren Anderson

I have ordered one of these before as well. They last 1-2 years in service with a Roomba in my experience.(i dont use my Roomba heavily but probably weekly or twice that). Its easy to install the battery and it charges right up etc. and then your roomba will run for 1-2 hours on a charge (more than it did when it was new actually). You'll have to replace it again in a couple years most likely but its worth it rather than buying a new one.