Eventhough I get your point, I don't think there's a "normal" time frame for drawing something.
Like it was mentioned before it really depends on the style, pose and how you color. A painterly style vs a anime style colors (basically one local color and one shade color) wouldn't be the same in regards of the time spent doing it (eventhough you're working with the same character/pose in both cases).
Adding to what's previously said, also you got to take into consideration that if you're working for yourself you could spend as much time as you want with a piece, but if you're working for somebody else, well that's another story...
When you start working for others (and it involves money) you realise that each commission it's a challenge, each it's a puzzle that you need to solve. Some you may do it in days, some may take you weeks. So you need to find a balance between meeting deadlines and doing a good job, sometimes you need to learn to compromise certain aspects that you wish you could spend longer on it, but to get the job done you need to cut them. That's the hardest thing I think, finding that balance between speed and quality.
So, in the end, I would work on my skills first, speed will come with time, the more you draw something, the more you know something, the faster and the better you will draw it.