The Parkinson’s law dictates that work expands to fill the available time. In this sense, the time spent on something behaves like a gas: it fills up the space.
Given that the work will take all the time allocated to be finished, we can either choose a low-intensity/high-time approach or a high-intensity/low-time approach to the work we do. I aim for Intensity in life, so I choose the second approach whenever I can.
A good way to combat this problem in projects is to create shorter deadlines for smaller tasks. Creating milestones that force us to finish tasks in a shorter time frame reduces the chance of dragging on the project for more time than it really needs.
I see this also in weight training. Since I’ve started to do a superset based full body split my training sessions are much more intense, but I spend way less time in the gym.
References
https://en.wikipedia.org/wiki/Parkinson%27s_law
https://www.youtube.com/watch?v=clDUHSsYs6o