It really depends on the complexity of the drawing.
I don't measure the exact time each drawing takes, but I usually draw in "sessions". Each session is about 3-4 hours.
The hairbun Taki I drew recently is relatively simple and has flat shading, so it can be finished in one session.
But something with more complex shading (like my pinned tktm drawing) might take two or three sessions to complete.
For complex drawings the process is usually like this:
- 1 session for sketching and clean-up/inking
- 1 session for coloring and shading
- If I'm not done there'll be another session for refining and fixing details, then adding special effects.
And the multiple sessions don't necessarily take place on the same day, I can start a drawing one day then continue it at a later date.