Well, I've shared the origin before, so forgive the repeat for any that read. But summarized: Had a weird fixation with feet and tickling when I was really young, like 8 years old or something like that. Played tickle tag with the neighbors, that sort of thing. And just became...weirdly obsessive with it. Then, puberty hit and bam: Foot Fetish and Tickling Fetish.
After that, I became FAR more obsessive with it. Christian upbringing, so naturally, sex drive went insane for a good while. Developed enough that I lost all desire for actual sex and found no enjoyment in it at all. All I wanted was to tickle feet.
I'm thirty three now and I've since calmed down a lot. They still remain a MAJOR turn on, beyond anything else, but I can have sex and enjoy it, even cum during it (which I could not before). I think hyper-fixation was really to blame there, thanks to my religious upbrining all about 'no sex before marriage' and such. But since I've gotten older, it's thankfully more relaxed.
I do enjoy tickling everywhere, feet obviously being a favorite. Foot fetish used to be bigger than it is, it has also seemed to calm some too. Still love, always will, but desire for the more 'worship' aspects (toe sucking, sole licking, etc) are extremely situational now.
For tickling, I think the only other real changes I've gone through somewhat recently would be a sudden, subtle desire to maybe experiment with being a lee with someone. It's a weird one for me, cause it flies in the face of my inherit 'dominant' role I play in relationships or FWB stuff. But all the same, something to explore. I ALSO kinda see the appeal in pits, more specifically pits as opposed to just other areas that aren't feet.
Hopefully that was at least mildly interesting to y'all.