Was it like that in ToEE? If it was I guess I never paid attention. Basically you just keep failing and you keep getting exp. At level 2, 5 characters all get 200 xp a pop. Quite a chunk for level 2 characters.
It was like that in TOEE, but generally failing to disable a trap repeatedly would kill at least the rogue working on it.
My understanding of this (from ToEE) was that the dice-rolls window says you are getting XP each time, but you aren't actually getting it after the first time.