When it happens depends on a lot of factors, including:
How fast your going
How soft/stiff the board is
How much dampening the board has
How long the board is
Camber or rocker profile
I've never felt anything but the slightest hint of chatter on my NS F1 at any speed or on any terrain. When it did sort of act like it might want to, it was while at high speed hitting some kind of small bump on really hard packed surface and being flat based. Of course, this is a VERY damp, relatively stiff board, and not full rocker, so I wouldn't expect it to chatter. Now thati think about it, the chatter onset thing started happening a couple of days before broke the nose...maybe that wasn't coincidence.
Other boards, don't have much experience with them, but I would expect it to chatter when flat if on a park style soft rocker with no damping and lots of pop. It's really a question of what you want out of a board.