People often ask me, “How long did it take you to paint that?” I have a variety of answers to this common question, some of which I've gleaned from other artists' musings on the subject.
I usually say something like “Oh, I work on it on and off for a week or two—maybe 8-10 hours total” though I don't keep track of or even think about how long I'm taking to paint something. The problem with this answer is that, to them, it might sound like I'm not working very hard or long on artwork that is priced in the thousands. I would like to say that it's taken me thirty years of working to get good enough to paint it in a short amount of time, which would be true! Years of experience means less time “fixing” things in the painting, plus knowing how to begin or lay the groundwork for future stages.
It is also true that I spend an equal amount of time not painting, but planning the composition and subject and then thinking about how I'm going to paint it and what colors to emphasize. I think it is of utmost importance to know what the painting is about. Whether working from life or photo references, it is connecting strongly with something about what you're looking at that is the essence of the painting, and this strong connection will carry you through to the end. You are painting your response to what inspired you to paint. For me, it can be something as small, subtle or vague as a suggestion of a light effect I can emphasize in the painting. Once I've started, I spend a lot of time just looking at it and thinking about how I'm going to proceed. I guess this counts as painting time too.
I am not offended when asked this question, but I do try to take the time to educate people on the process if they're interested enough to ask it!