[Magic] Loophole in the “Tickle” spell

[VIVIT]

One the sillier spells in GURPS Magic is Tickle—a Magery-0 Body Control spell with a prerequisite count of 2 that lets you afflict the subject with a seizure (!?) for its duration of one minute. This is surprisingly potent for such a low-level spell, but it's balanced by the fact that it requires continual concentration—the idea presumably being that the caster must actively exert some sort of telekinesis-like force to do the tickling.

There's one problem, though: spells that require active concentration don't terminate when you stop concentrating. You can resume them at any time. This seems to mean that with a single casting of this spell, you can inflict several seizures by concentrating intermittently. Since a seizure inflicts 1d fatigue when it ends, you could, in theory, use this spell to very quickly drain someone of all FP.

Incapacitating conditions are pretty severe in the first place, so this may not be quite as unbalancing as it seems, but it still feels kind of abusive. And while it's trivial to say, "No, it doesn't work that way," it's not so trivial say how it's supposed to work instead. How long does a seizure have to be before it fatigues you? Do shorter seizures inflict less fatigue? Do longer seizures inflict more fatigue? The seizure condition as described in Basic Set doesn't seem to be intended for a maintainable, variable-length effect like this.

Have you ever seen this spell if in any of your campaigns, and if, how did it work out? Has anyone tried anything weird like this with it before?