Got a friend who did a couple of degrees and has a masters in photography. Currently a creative director so it didnt do her any harm. I think if you're doing something relevant then its all valid to your development within the industry.
But on the other hand, you could spend that time gaining valuable hands-on commercial experience...
But if you wanna learn, go for it. Its probably easier to go straight into it while you're in the learning mind-set than having a break in your career.
So, to sum up... i dunno