I think that could also apply to any area of the body that's way too ticklish. It could also depend on how the lee likes being tickled too.
My feet are the only part of me that any ler would probably want to work on, as the rest of me, while still somewhat ticklish, wouldn't produce near the effect that tickling my feet would.
My predicament is that I can't take hard feet tickling very long anymore. Call it age, or whatever, I dunno. I would tend to pass out after a short while. I know this cause it's happened twice to me, and it's no fun, I can tell you!
Now, having said that, while slow, long, drawn out tickling, would start out feeling pretty good, if it became non-stop, after a while it would become so intense that I would have to wonder if passing out isn't a better option.😛 Either way, I would have to be restrained, for the safety of all concerned.
So, I can see that extremely ticklish feet could definitely present a problem. Hope this reply is kind of what you were looking for.