My simple opinion: do not load your nervous system with too much electricity! According to my own experience, even 7-20-7-20-7 is loading me enough (hearth pain, headache, etc). Understand, that all the processes in the body are regulated by the CNS via weak electrical signals. In this fine ballanced electrical system, you put significantly bigger load of pulsing DC, which is interfering the rest of the "data-flow system". Of course, as a creation of God, the human body is too good and filter these interferences in communication, but do not overdo it.