Changes in momentum make it interesting. Ever notice a player's confidence start to grow by a single great shot? How does the other guy respond? Does his confidence start to erode, or does he meet the challenge? Ever suffer a setback in life and pull yer self up by your bootstraps? Ever take a dive in life of biblical proportions when you thought you had all your stuff together and that you were the shiznit? Same thing happens on the tennis court. Drama.....Yeah.
Who wants to watch machines play a perfect game?
Metaphors. They are all around you. Embrace them.
I get what u try to say, but momentums of 20 seconds are just awful and lame.