Dana, I've used TENS with circular electrodes around each nipple for at least 6 months. At first it was very stimulating then gradually the current had to be increased for the same stimulation. The area was getting less responsive, but I continued. I noticed the nipple/areola areas getting more erect and hard so I discontinued it because the suppleness was lost. You could possibly stimulate lactation if TENS was used on a regular schedule 6 time a day. So I was caught between wet shirts or nipple projection through my shirts. I wasn't ready for either.
Good luck, L^te