I often take tennis lessons and then I want to go and practice on my ball machine for a couple of hours. Today I was playing and a couple walked up and was wanting to play. I had been playing about 45 minutes, but I needed to practice about another 45 minutes to an hour to get all of the reps I have to get in after taking the tennis lesson. How much time should I have taken to continue playing in that situation? (I should probably note, that I offered them directions to other courts that were pretty close, if they didn't want to wait). What if someone walks up and I'm playing doubles or singles? Thanks!