Yep, I was almost exactly thinking of "work expands to fill the time", plus maybe a bit of "people take more and longer breaks when they work more hours". It's

Yep, I was almost exactly thinking of "work expands to fill the time", plus maybe a bit of "people take more and longer breaks when they work more hours". It's not a huge distinction, but I think "increased productivity" makes less sense as more output for an hour's work, and more sense as shaving off unproductive time.