1 hour 18 minutes isn't bad at all! I can easily wind up spending three on a single panel if it's quite complex. Usually if I have to set a new palette for it, or if it's an establishing shot with heaps of background details. (I try to balance it out by spending less time on headshots.)
Good art takes time. Unless you have deadlines, it's good to take that time to explore. Especially while you're learning.