I ask the Hobby Quadrature Gurus out there, 
What is the shortest sampling interval you’ve ever used? And what is the interval you prefer?
We’re (Robix.com) doing back-of-napkin design on a new quadrature encoder that fits within a standard size Hitec Servo, with the two quadrature wires exiting along with yellow/red/black. Probably we will use HS422 since it is inexpensive and rugged.
Robix sells its complete robot sets only to educational institutions, but some of our parts, most notably our gripper, are used in quantity by highly respected robot kit companies, 
and are also sold through Jameco and other outlets. So, with our quadrature design we’d like to again satisfy the needs of the hobby robot rowdies as well as our own more conventional educational customers.
Here’s the thing: Our Usbor controller does quadrature sampling at 15ms intervals, which implies a certain optimal slot or vane spacing. However, hobby-type designs have potential for much smaller transition intervals, that is, much higher speeds, implying a different optimal slot or vane spacing. Robix would like to be able to satisfy both the lower-speed educational user and the higher-speed hobby user. We may, for instance, mold two interchangeable vanes.
SO: I’m asking the Hobby Quadrature Gurus out there, What is the shortest sampling interval you’ve ever used? And what is the interval you prefer?