What you are describing is a pretty poor pairing interview process. I did a bunch of really frustrating whiteboard type interviews and sudo pairing interviews like you describe before interviewing for my current position [1].
The screen is a one hour onsite pairing session followed by a final round that is a day of pairing using a proper workstation: One computer, two monitors and two sets of mice/keyboards. You pair with one person in the morning and another in the afternoon. It's very relaxed (you take turns "driving") and it gives you and the interviewers a lot more information about each other and your potential place of work. It also gives you enough time to adjust to the process if you are nervous. I don't think I'd do it any other way going forward.
The screen is a one hour onsite pairing session followed by a final round that is a day of pairing using a proper workstation: One computer, two monitors and two sets of mice/keyboards. You pair with one person in the morning and another in the afternoon. It's very relaxed (you take turns "driving") and it gives you and the interviewers a lot more information about each other and your potential place of work. It also gives you enough time to adjust to the process if you are nervous. I don't think I'd do it any other way going forward.
[1] http://pivotal.io/careers