How Long?

I've been asked, "How long did it take you to make that"? Well, I say, about 30 years or so and they look at me as if I had two heads. I'm not offended by the question. I'm just wondering if the revealed time would make any difference in their judgement.
I'm not one of those who punch in/out when they paint. I've tried keeping records only to find, it is hard to put a time on the thinking, organizing, gathering subjects, lighting, etc., before I even start the drawing.
The painting I am currently working on, I knew would be out of my comfort zone. I had to restart several areas. I would have to account for that time. If you bring your car to get fixed and they don't fix it on the first try, you still have to pay for any additional repairs. This is a strange metaphor comparing an artist to a mechanic but it is kind of the same thing.  This probably happens to a lot of artists no matter what their level is. Shit happens as they say. Some times even the most planned paintings go astray.
So, maybe a better question would be, "How long have you been painting"? That way it encompasses a whole more. If one really likes a painting, it shouldn't matter how long it took to create. I know the question is out of innocence and just a matter of making conversation but I always find that one puzzling.