I had a discussion with a workmate today which resulted in me putting my money where my mouth is.
I’m currently through my own choice working 6 on 4 off, consequently paying back hours etc isn’t a problem. Where our disagreement came from is; I finished work pm last Sunday, did not start back till am Friday, I said to my mate that if I felt the urge I could actually do 6x 15hrs spreadovers back to back because the “week” doesn’t start till midnight Sunday. He disagreed saying that my week started on my first day back (Friday). I hope I’ve worded that ok, but basically my opinion is that I’m spreading my 6 days work over a two week period, if that makes sense.
Please agree with me, cos there’s enough to pay for a decent night out riding on this! 
You can only reduce three times between weekly rest periods making it impossible to do six back-to-back 15 hour ‘spreadovers’, unless using the split rest option. Hope your mate enjoys the night out!