<p>I have two faculty members that I am interested in rotating with, and have already setup my first rotation (to begin in a month) with one. Is it too early to contact the other one to setup my next rotation for the fall? If it is, what is the appropriate time to contact the person I want to rotate with next?</p>
<p>It likely depends on the professor and his/her personal style. I met my now-advisor in the spring of my senior year of undergrad and asked about setting up a rotation in the fall, and he looked at me like I had two heads. 
Not an advance-planner.</p>
<p>You may as well contact the second and say that you’re interested in a rotation in the fall. He or she will most likely either start talking about setting one up now, or will ask you to email back at a later date.</p>
<p>It’s your career. Do this as early as you like.</p>