Last year an instructor asked me whether two short breaks or one long one was the better strategy during a long webcast. Because I didn’t have an informed opinion, I encouraged her to let them decide via a polling question. They opted for a single, longer break–one twenty-minute break instead of two tens.
I was talking to the same instructor recently and she noted that she got a lot of feedback on evaluations that twenty minutes was too long for a break, so she’s going to shorten it this year. So really the question appears not to be, “Do you want your break time in one chunk or two?” But rather, “Do you want one break or two?” The implication here is that if they accept less break time, the class will end earlier. Absent a good reason to do otherwise, she should honor the feedback and have a short, single break, but then end a little early to fulfill her side of the bargain.