I need the output of the pot to go from 0 to 10K over a 500ms time. Hence 1K will provide the 64 steps in that time. Depending on the CS and U/D pins will determine if it counts up or down (obviously) but once it reaches the limit further clock pulses won't do it harm. I can estimate at approx 500ms I can remove CS until it need to count in the opposite direction.