How often to demagnetize mc cartridges?


Just bought a used sumiko fluxbuster and demagnetized my Lyra Etna for the first time.  Pretty nice improvements in sound!  How often should cartridges be demagnetized?
wcheng2
NEVER demagnetize anything which already has a magnet inside it for its normal operation.  Otherwise you will destroy/weaken the magnet.  This includes moving coil, moving magnet cartridges and speakers as well as your credit cards :)
Fluxbuster works fine on HOMCs.
Use it whenever you think it will improve the SQ. No set answer, every system and ears are unique.
Did you get the manual?