It depends on the settings and length of the session.
I now find that after using my tens for a few months, it does not seem as effective or as intense as first time around.
The first time I placed the pads on my penis, and on a low setting WOW!!! I came within thirty seconds. My whole body seemed to go into a spasm. Now, I need higher settings and can go on stimming for several hours. After a long session, yes, my cock seems to be a bit numb, and the tingling can last until the next day.
I am worried that I am overdoing it, also, am I somehow damaging the nerves? I crave for more and more power, more sensation. I use my tens with the tens and ems settings. I like the dull, thumping pulse at times, as it is painful. The pain actually makes me cum, simply because I am into cbt.
After a day or two, the tingling has gone, my penis feels normal again and I become more imaginative with my homemade attachments, using a strong thick steel wire to wrap around the sulcul groove under the glans, also makin a loop so it inserts into the urethra. I also clamp the shaft tight while I ramp up the settings. This gives me an incredible orgasm as it seems to increase the sensation through the shaft and into the glans.