They did this a couple years ago at PCL. Dropped the day off average to just over 11, 94 hour average block lines, and mostly non-commutable.
That month, the sick calls went up by 400%. Yeah, you read that right. The company ended up canceling HUGE numbers of flights for staffing.
It wasn't an organized job action; the individual pilots were simply too fatigued to fly those kinds of schedules after doing one or two rotations of it, and the company heard us loud and clear.
The next month the lines improved DRAMATICALLY and they started hiring massive numbers of pilots to properly staff the airline. Turned out to be a pretty decent summer.
Morale of the story: take the time off you need in order to start a long trip like that rested and ready for duty. If it affects their operation... too d*mn bad. Guess they should have thought about that before they staffed so low as to require those kinds of lines.