Good Morning,

"I would expect that if you are working close to capacity, the longest developed film might use an unequal share of the developer's activity, before the other film(s) is/are added."

Matt--You are probably correct. I think I avoid that most of that problem by starting with all the films and then removing early any needing a shorter time. For example, if one film needs seven minutes and the other needs nine minutes, I suspect that, with most of the development is complete after seven minutes, any extra pep available to the nine-minute film probably makes little difference. At least I've never encountered a problem. Obviously, there could be a difference if the developing times vary widely, say one film at five minutes and another at fifteen. With that great a discrepancy, I'd probably develop separately anyway, since the time working in complete darkness would be considerable.