Work expands so as to fill the time available for its completion - Parkinson's Law
I remember watching an episode of The Simpsons years ago, where the high-IQ types took over Springfield. One of the first orders of business was to remove the green light from all traffic signals. The thinking here was that, everyone would get to their destination faster since drivers tend to speed through yellow lights to avoid stopping and waiting.
We engage in similar behaviors in the workplace. "I have all week to get that report done". "The system doesn't go live until Monday, I'll do all of my testing over the weekend". "Sorry, can't chat, there's a code freeze at 5pm and I still have to wrap-up this feature". We tend to operate our lives in a green light mode, where everything is fine and we have all the time we could ever need to accomplish a task. Until we don't, then the panic starts.
In every area of our lives, deadlines drive behavior. When we have something due soon, our minds become focused on the task at hand. There is just enough tension created to cause us to act. This can be used to our advantage by creating a series of smart, well thought out, deadlines to help guide desired behavior over the entire life of a project - instead of a single monolithic deadline looming at the end.
When running a team, set short and reasonable deadlines that lead everyone to a bigger goal. Make cutoff dates clear where no additional updates can be made to the system after a specified point-in-time. Give your testers, and users, and other stakeholders, deadlines to complete their tasks - and be sure to leave some wiggle room for the guy in the back who doesn't look at anything until two days before the end of a release.
Leveraging deadlines in a way that creates productive tension will help teams function effectively, and with more discipline. Frequent deadlines also set better, more realistic, expectations for business stakeholders and you can more easily tell if your project is going off track. I think Professor Frink was onto something here.