The CM's also have wives, husbands and families, too. So it is a strain on all of us.
But IMO the most important aspect of a scenario is the retention of the player base during the scenario. Some people may not prefer two frames per day, but the fact is that since we switched to this format, the attendance for the last two frames has been consistently much higher than when we ran one frame per day. It is a strain on everyone involved, but the numbers don't lie. If people are there for frame one, nearly all will remain for frame two if it's immediately following.
That being said, we are going to try a one frame per day format for the next scenario, as Jordi mentioned. In the future, the format will probably vary depending on how much planning is needed in between frames. BoB shouldn't need too much since no base capture is involved.