No They are a waste of time- you will not find any difference after doing it and I have empirical data as well. The motors put out 100 times the field intensity that the heads can have on them and all the parts in the tape path are not magnetic retaining anyway.
Everclear also works great at cleaning heads also. Organic, non toxic and if you get frustrated working on your tape decks can be used to help sooth stress. Works for me.
