Numerous artists of the past would spend as long as a year on finishing a painting. I think besides the individual own comfort zone or degree of experience, it also depends on the degree of detail in clothing and background setting. The more elaborate a work is, the more attention it needs.
Obviously the approach also determines speed, when layer upon layer is built through glazing, by nature you have to wait until the canvas is ready.
I don't perform well under time pressure either and prefer to take my jolly good time. This can sometimes be a very long time.
