Thanks for your input. I just wanted to set a goal to work up to in minutes of jumping rope. Another way I could have asked my question:
Imagine a good 5.5 player who frequently jumps rope.... he can last 3 sets playing high level tennis without real fatigue kicking in. How many minutes do you think he can jump rope for at a minimum if he tries his best?
(The answer is obviously not 2 minutes. If he can only manage to reach 2 minutes of jumping rope at 120 skips a minute, no way he could last 3 sets without real fatigue kicking in)
so how many minutes continuously, at 120 skips a minute, do you think he can jump rope at a minimum

?
I know there's no correct answer but I just wanted to have some opinions about it. And maybe I'm just an idiot to ask that question, sorry.