120 minutes is how much you might be able to get under optimal conditions assuming a battery that's close to brand new, a wide open room with nothing for the robot to get stuck on, and a floor that's already clean enough that it doesn't need to ramp up the suction for targeted cleaning. In other words, it's probably more than you'll get in day to day use. I wouldn't be that concerned about it though. The biggest advantage to having a robot with active navigation like this is that it knows where it was when it ran out of battery. So when it gets low it stops, returns to its dock, then picks up where it left off once it's gotten enough charge to finish the job. So long as it doesn't end up cut off from its charging base by a closed door or the like, it can stick with a cleaning job more or less indefinitely.