I've heard gathering fatigue sets in after a while, reducing your rate of getting items, or even upright stopping you from getting anything, sort of like fishing fatigue from FFXI. What I want to know is:

1: How many gatherings do I have to do before this happens?
2: Is this one fatigue across all three disciplines, or does each one have their own fatigue?
3: Does gathering with my off-hand tool affect it?