For the longer time limit, it's often tempting to start focusing on details right from the start. This causes the artist to forget about the broad proportions and gesture. Try using the extra time to get the overall gesture and proportions right. I've heard some artists limit themselves to using purely "C" (curves) "S" (wavy curve) "I" (straight line) to help them achieve this. Proko on youtube has an excellent video on this.
Hi Jeremy! Looking good so far. :) Adding on to darkover's advice, maybe you could focus on using less motions of your pen to get your gestures down? They look very over-saturated with repeat sketch lines that don't immediately try to get the action lines down. Maybe this post is helpful?