I'm going to add some stuff here that's not necessarily in line with what others have said. Take it not as a rule, but another perspective.
My suggestion to the topic of "what should I be doing?" is figure out where you want to go first. The reason being is that traditional art training bends the look of your work to a certain way (realism) and it's extremely difficult to get rid of that thinking once it's ingrained. Take a look at these examples below. One is a figure drawing in the style I learned it, the next is an industrial design technique based style which is very distinct and almost all industrial design students end up with, and the last is a folk style painting by a book illustrator.
The training for each of these styles could be very different. The exercises you do will (and should) lead you to where you want to be as a pro. It would be a sad day if I directed this folk painter to do some perspective exercises. The same way it wouldn't be as helpful to direct the ID student to focus on life drawing. (BTW: I LOVE drawing the figure, I'm not saying it doesn't have any value at all because it does). I'm just talking about what you primarily focus on.
So if you are going to be a concept artist, focus on environments, props, and character design (which includes life drawing). Almost all concept artists would be benefited by choosing industrial design type sketching to focus on (form based drawing, drawing through objects, etc.). If you are going to do realism, by all means get your butt to a figure drawing session, If you are loving quirky work that is way off perspective, it may not totally be necessary to go through traditional training. The more important studies here may be graphic design, composition and color control.
Anyway, to make a long story short, pick what you want to do, then do that. : )
