Attitudes and Sensitivity
I have had an intense tickle fetish since long before I even knew what that meant, probably starting about age ten. My wife has known about this little quirk in my character, again, I'd guess, since before I knew what it was all about. I've been tickling her at every opportunity for about three decades (since she was only my girl friend).
I have no way of knowing how this works for tickle people that don't have the "fetish." Those of us that do share a "feeling" about it that likely could never be explained to others. I knew by my mid-thirties that this activity can only be fully enjoyed AND appreciated by adults. That is, it's a phenomenon that is wasted on kids, at least it was on me. Now I believe it helps me stay young in spirit, and, if Memorial Day is any evidence, there is still enough of the tease in the wife to provoke my desires despite the fact that she gets the results worse every year and every time. I have learned through experience how to tickle her for maximum effect.
As to effect, different people will react differently to it, but my ticklee certainly hasn't lost any ticklishness over the years. She is extremely ticklish from head to toes and her worst spots are her upper ribs and armpits, as well as her upper inner thighs. I usually save these spots for last. Her reaction rarely disappoints me, and, maybe because I know her body better than she knows her own, I usually get a reaction up to silent laughter most of the time these days.
I'd say I'm one of the luckiest tickle people anywhere, in that I have never lost even the tiniest desire to tickle, and I have a wife that has always put up with me. I hope and suspect I'll be tickling her half to death for another three decades.