Some, if not most monitors will degauss themselves when you switch them on. You can tell by the noise it makes when its just switched on. If you're using one of these monitors, and you don't keep your computer on 24-7(or for long periods of time), or you don't move it around a lot of bring it to contact with magnetic objects, you don't really need to worry about degaussing. Perhaps once in a while, but definitely not frequently.