"How long did it take you to make that?"
Regardless of the medium, people seem to have an innate curiousity about how much time is spent working on a given piece. I expect it's a genuine interest in the actual process, which is outside their experience. An artist usually has a ballpark figure of the hours (days, weeks, etc.) they clocked in creating an given work; which of course doesn't take into account the years spent practicing their craft or planning the project. All of which certainly contribute to the end result. So the answer to that question is dependant upon a lot of variables, many of which are difficult to quantify.
Artists work at an individual pace; regardless of medium or methodology. While it is certainly possible to overwork a piece, I don't feel that there is such a thing as spending too much time on art. The creator spends as much time as they need to complete the work as they see fit. Period.
Speed of creative pursuit is determined by: artistic temperment.
I am a slow painter. This doesn't mean that when I put pen or brush to a surface I move at a glacial rate. I prefer to work at a measured pace over a stretch of days or weeks, rather than racing to cross an arbitrary finish line. While working on a fairly modest scale my method can be viewed as tedious and measured. The thousands of tiny dots or lines I have chosen to draw, take time.
"I don't know how you have the patience!", is something I hear a lot.
I am as guilty of impatience as the next person; particularly when a webrowser is lagging or the line-up at the coffee shop is one too many people long. It strikes me that the most of our world seems to be stuck in fast forward mode.
Making art doesn't have to be.
For me, creating art slowly is an exercise in calm; although I hesitate to label it meditative. Even slow art has it's 'argh' moments. Generally it allows one time to reflect and contemplate the work at each stage of the process. There is value in stepping away from what you are doing and looking at it with fresh eyes later. Hitting the pause button on 'creating' allows the artist to evaluate the work done & make adjustments if required. Admittedly it has a side benefit: reducing incidents of smeared ink or paint.
Mostly I work slowly, both in medium and method; because it makes me happy.
And who wouldn't make time for happiness if they could?