How often to demagnetize mc cartridges?

@lewm , would you say that I need to rethink my protocol as stated above? My cartridges I am using in rotation are the DRTxv1s, ZYX original copper Universe, Shelter 901, Koetsu RSP, AT ART9 and ART7 and a Grace F9 SS optimum line contact, the latter MM I do not demag. I have followed this protocol with no derogatory results, that I can tell, but wonder if what I don't know might be hurting me in this matter. Looking forward to your response, not trying to bait you on this, do believe that it is pertinent to the OP. Thanks

I don't know how the cartridges on your extensive list are made.  Except for the ART7, which I do know has an amorphous core coil. I think that one contains no iron, no magnetic materials, does not need fluxbusting ever.  MM cartridges, of course, should NEVER be demagnetized, as you may kill the entire beast very quickly.  I have the sameSS-modified Grace, based on a Ruby original.  It is excellent. As long as you don't demag an MM, I don't think you can do harm to an MC by fluxbusting. I use the Cardas test LP once in a while for that purpose.

I use the Cardas Sweep Record every few months and find that it is
worthwhile to do. But my limited understanding is that this is a very
different (and probably more lightweight) process than the demagnetization provided by the Sumiko Fluxbuster and that kind of direct demagnetization, particularly if overdone, can be harmful. 

AJ Van den Hul, for example, strongly recommends against 
demagnetization with stuff like the fluxbuster. 

There are some interesting comments below from JCarr of 
Lyra from a post at Audioasylum. 

https://db.audioasylum.com/cgi/m.mpl?forum=vinyl&n=61192&highlight=degaussing+demagnetizing&r=&session=http://

I was told by Dynavector that their cartridges do not need to be demagnetized. I have a ZYX that I have never demagnetized - sounds fine to me. 

Never is the correct answer. Worse than stupid concept perpetrated by people who have no idea what they are talking about. If you have a reel to reel you can demagnetize your tape heads. If you don't, throw that thing in the garbage. Your going to hurt yourself.