As a Front-End developer and using livereloading whenever I do changes to html, css or js it is actually a time saver to have two monitors, one with the IDE on full screen and the other with the browser. This saves me a lot of time, I had a teacher that taught us about 3d stuff he said that maya had a tool that with one keystroke you could repeat the action of the last tool you used... he said that it saved you around 2 - 5 seconds from doing or selecting again the tool and recreating the action and when it was a very small project it did not matter at all.... but when you were on a very long and heavy project seconds would turn to minutes, minutes to hours and hours to days... so yes having two monitors is actually a time saver but when using an iMac is kind of difficult to plug in or using two, so at work I'm stuck with one :(