Originally Posted by UCSF2012
Increased dwell time increases power but decreases spin.
It's largely irrelevant whether the human brain can sense ball impact as it's occuring. It's not like you're gonna change your swing during the split second of impact. (Except for touch volleys.)
In fact, your nervous system is fast enough to detect the split second the ball hits the racket. The nervous system is ridiculously fast. The basis for touch/drop volleys is softening up on the grip during impact, so the ball dies.
Edit: not even worth it.
To the OP: dwell time is not an important TW parameter because there is no way to state it as the measure of anything. The TW spin parameters are stiffness, ball-string friction, string-string friction and perhaps one more. None are quantified as the time the ball spends on the strings.