One of my friends told me that when Kvish Shesh - "Tollway rte. 6" in Israel was completed, there was some concern about cars driving on the road on Shabbat. The CEO of Derech Eretz, the company that manages the road suggested that drivers should speed on Shabbat so that they spend less time desecrating Shabbat.
When I heard this, granted, I was surprised that apparently there was no concern about the safety concerns of speeding on the highway. But, I have also never heard that chilul Shabbat involves a "time duration". E.g. if I write a letter on Shabbat, I believe that I have violated a melacha once whether it takes me 3 minutes or hours.
Is there any validity to this notion of lessening the amount of time you are mechalel Shabbat?