Use compressed air to blow out dust/wool from intake and exhaust ports and change the carbon brushes when you need to. You will know when you will need to change the brushes as the buffer will start to act up. eg: motor stutters/turns on and off as the buffer is in use.
You will also sometimes need to fix power cord as the constant flexing will break the inner wires. You shouldn't really worry about this as its a very easy fix and it will take a while for it to happen(took my buffer 2 years of constant use.)