Moving Coil Cartridge Demagnetizing

How important is it to demagnetize moving coil cartridges? How often should it be done? Any advice appreciated!
you won't realize what a difference it makes to demagnatize your moving coil cartridge until you do it for the first time. i prefer the aesthetix (benz) demagnatizer, finding it easier to use than my "classic" fluxbuster. i try to demagnitize after about 10-15 hrs of playtime.
Does the same apply to MM carts?
You cannot demagnatize a MM cartridge the way you do a MC without damage to the cartridge. Correct me if I am wrong, but I believe that the stylus must be removed from the body to avoid damage to the cartridge.
I use the fluxbuster.I have a Cardas ter. block that has rcas from the phono wire.No need to remove the cartridge. I also have the Cardas 'sweep' for me;I use both.
I own the Cardas 'sweep' disc, and it works good for me, about $24.00. Has anyone compared the cardas disc to an aesthetix (benz) demagnatizer? A lot more mula.