FlapsOne, you said:
'I, and everyone else, work 6 on 3 off.'
If you think that is completely honest see Airbrakes' post above just for starters, it is not so.
If one of the three days is a 'Flexi day' its not a day off!
I never suggested 7 on 2 off was the normal state of affairs, but it's not unusual either, I had one this month, proving your quote to be incorrect.