It is one of the joys of graduate school (and a great advisor) to have a flexible schedule.
One of the articles I came across, however, an editorial in Nature asks, Do scientists need a PhD?
I suppose my answer would be the same as concluded in the paper:
"The answer is not clear-cut."
The process is highly individual, and the end goals can be very different, especially depending on the field. For me, personally, I would not have been able to learn about so many different research paths without coming to graduate school. In the community I grew up in, I didn't really consider being a professional scientist and graduate school has really opened the door to the multitude of paths available for a career scientist (in industry, government, public policy, and academia - both large universities and small colleges). Without going to graduate school, I do not think I would have been exposed to so many different ways of approaching and interpreting scientific research and would not have been pushed to develop my critical thinking skills.
So, for me, for the career path I want, yes, this scientist needs a PhD.