A lot of time..and depends on how many coatings, certain walls need more paint than the other so that your can tell visually. Touch up is very painful, the corner and the edge. Also if you are not very experience, the taping is quite frustrating because you want to make sure the line is straight. Washroom..tiny little space, need special type of paint.
I spent almost 700 at Benjamin Moore. By the way, dont be cheap on the brush, you will see a huge difference. At the end, I paid somebody to finish the job for me -only the stairs.
I dragged it for almost half a year.