In your model, you're giving staff 2 hours to:
Eat
Change
Clean the room or if you're lucky, a cleaner will come and vacuum for you (Pencil sharpenings are the worst)
Ensure displays haven't been damaged already (inevitable) so run around with staple gun
Tidy books and resources in the room
Visit the bathroom
Set up resources to show to parents - pupil work, text books, exam materials, SMART board, pictures of lessons/activities
Move car because SLT want the car park free for prospective parents to use
Show student volunteers what you want them to do
And that's just for my classroom part! For PE it's a whole other ball game getting tonnes of equipment out, putting down protective floors, showing student leaders what to do, ensuring areas are roped off for safety, tidying up changing rooms, fixing display boards (again, always getting knocked by bags/shoulders etc), setting up a projector to show pictures and videos.
Oh and don't forget you've been in teaching and done your normal day of work... perhaps a little break might be nice!
I think having a few extra hours to arrange everything and ensure staff wellbeing can only be a good idea.