I think the shot clock is a good idea because some people do take forever, for no good reason, leading me to shout "Just fucking serve!!!" at the tv 
But it should be used consistently, although I appreciate that, between umpires, this is easier said than done! There should also be a bit of common sense applied. If you're into the 3rd or 4th hour of a match, being played in 80 degrees heat, and you've just had a 20 shot rally, clearly a bit more recovery time is sensible. But again, consistency is required and the difference between Aurelie and Mo, for example, can be vast 
