Hey, thank you. Okay, I will answer honestly, based on how it applies to me.
The first one with Black Swan took me 1.5 hours. I didn’t keep track of how much time the lineart took, but if I were to guess maybe 1 hour? Coloring was very fast and loose. The time really starts to fly by when you get to tweaking some details that probably nobody will notice 
The second one with Sparkle was 1 hour 15 minutes. Again, tweaking and adding some detail is probably what took the last 20 minutes or so. I can make pretty big corrections even at a very late stage, because as you add more lines you notice better if the balance is wrong.
So yeah, I would say this is slow and difficult for me. For every good drawing I have like five bad ones. I know copying is nothing to write home about, that’s why I’m always very clear when I draw a copy, but it still takes skill and a lot of attention. What I’m trying to achieve here is to always draw with a good reference to really drill those proportions into my brain and have a good eye for the balance. My hope is that at some point it will help me notice mistakes and draw better original drawings.
Also these two pieces are not the best practice, honestly. My current limitation – still, after a year! – is character drawing, especially the face. I’m rather confident with colors and can get decent results, but my work is held back by mediocre head balance and various mistakes, so I want to fix that. It would be more efficient to not push a drawing that far, to shading and details, and instead draw a larger number of simpler sketches, to get enough reps in. However, once in a while I need to draw something beautiful to convince myself that I still can.
Yeah, that’s one thing that gets me with drawing
You just cannot assume skill. At least, at my level. If I get too complacent and sloppy, everything falls apart and I get demotivated. I know I should be drawing 2x, or 3x more than I do now, but I don’t want to get burned out either. I hope that at some point I can raise my skill enough to draw simple sketches effortlessly and be able to focus more on artistic expression or interesting ideas instead of the technical side. Well, it’s a journey… 