RE: How fast is to fast?
Other factors will be the F.O.C. of the arrow, how well the bow is tuned, size and amount of helical on fletching, and whether you are using fingers or a release.
I don' t think anyone can give you a number that will apply in all situations. In fact , the number is probably at least slightly different for everyone. I would also guess that given the perfect setup and equipment, the maximum speed is probably a lot faster than what we' re shooting now.