I think about this in terms of how much clock time has elapsed versus how much working time I spend on something - i.e. I am very often able to trade an increase in clock time elapsed (taking more breaks) for a decrease in working time, and vice versa.

As with most things, this comes with diminishing returns as you push toward minimizing one over the other.

Sometimes, even negative returns, e.g. because of increased context switching costs, or confusion and general malaise caused by staring at something for too long.