I didn't read it all but
1 extractor and 4 roots is about right if you collect it religiously. Its speed depends on how much you sucked out, so you can either move root every time for max speed or leave it be and come back less often. I just leave it on a root until dry and then move it.
by the time you have drained 3 full roots to nothing the first one should be back up and running again.
I got more than I needed off a 3 root farm, but I wish there were 1 more in a reasonable distance.