I think the answer would depend to a significant degree on how well the AI program worked. A really good AI program would not only alternate and vary the tickling motions, but would also monitor the victim's response and modify what it was doing based on that, so that the tickling became more and more effective with time, and so that it was also able to adjust to changes in the victim's response (e.g., a victim might be able to resist tickling for awhile in some spots by tensing their muscles, but this ability might decline as the victim got tired or as they began to lose control of their muscles because their nervous system was so overwhelmed with tickling sensations).
I also can't understand why anyone would build a machine with multiple appendages and have it concentrate on only one ticklish spot. If I were building the machine, I'd have it attack all of the victim's known ticklish spots at the same time, and look for new ones that the victim didn't even know about.
I'd also have the machine measure the victim's pulse, blood pressure, and respiration so that it could determine when the victim was about to lose consciousness (perhaps from being unable to get a breath in) and automatically give them a break of about a minute to let them catch their breath (so that they didn't miss out on any of the fun 😉 ).
Instead of a safeword, I'd prefer that I had to estimate in advance how long I thought I could stand it, and then be gagged so that I had no way to change my mind once the tickling began. Part of the fun would be being completely unable to move and being tickled by a machine that I knew wouldn't get tired or bored and was going to get more and more effective at tickling me as time went on, and knowing that there was no way I could make it stop until the time I had agreed to in advance was up.
