Research in an Interdisciplinary Field

I came across this interesting article that Jonathan Lazar has contributed to the interaction magazine about why we as HCI researchers should think about taking a "gap year" and spend the time working/studying/researching in another field. He points out it's beneficial

HCI (Human Computer Interaction) is interdisciplinary and multidisciplinary by definition; you need to understand humans AND computers. And when I read the article, a couple of questions arose:

1. Isn't this something only a tenured professor can afford? Can Ph.D. students with specific funding projects or professors under their tenure clock also do this?
2. How much breadth do we need to have? and once you span to another field, how much depth should you strive for? I mean it's already impossible to know everything in one field, right?

Don't have clear answers to these questions, but would be interested to know what others think.