Use the Free Space Check to warn you if the system is running out of space.
Click the right mouse button on the Remote Notification Program. (That’s the little icon on the bottom right of your Windows Task Bar i.e. the bit next to the clock).
Select the Drive that stores LUMBERJACK and set the free space to, at least, the maximum size of a monthly backup. If you have bags of space, set the limit higher. This will ensure that you are notified if disk space is low.