Try placing the charge base in a few different spots and see if your Neato has a preference. No matter where you position its base, the robot should clean the entire area. You may witness subtle differences in its performance and cleaning paths from location to location.
Make sure you place the charge base in an open area with at least 3 feet of open space available on either side of it. This will help the robot locate and dock with the charge base successfully after a cleaning cycle.
NOTE: 3 feet from a corner in a room is generally a good spot since the on board vision system can use a perpendicular wall as a good signpost for docking.