How much time do you spend actually shooting a single look? is almost certainly too broad and opinion-based. Yet, it's clearly about photography and a respite from the common questions about gear and the technicalities of aperture and etc.
Can we make this question something that will work on Stack Exchange (and also preserve its spirit)?
It's not possible to separate the question from opinion without turning it into an entirely different question. I am unable to discern a reason for the question beyond discussion. There is no objective answer.
How long do you spend... ?
This portion makes the answer entirely dependant on who is being asked. Some people may spend their entire careers working on a "look", while others are more whimsical.
... shooting a single look?
What counts as a "single look"? -- What camera settings are allowed to change? Can the lens change? Can the subject change? Can the pose change? Can the environment change?
Answers to above questions may (again) be entirely personal to the writer (opinion).
Further, does post processing matter? Depending on the answer, the entirety of a photoshoot could be considered a "single look" or not. At the extreme, every single frame could be differentially processed into a different "look", and the answer could be as short as the shutter speed for each of those frames.
While I think that the question is interesting, I agree with xiota on the opinion/personal-part and the definition of look-part, but I think it is a problem of broadness, too:
A press photographer will spend a few seconds at worst (less time = better), while I know people that spent a whole summer - even a year - for a single project.
Are we talking press? Landscape? Portraits? Studio? Outdoor? Money-style professional? Ars-artis-gratia-style professional? Serious hobbyist? Instagram? Holiday with family?
I would/will spend different times on look development in each of them. And not even then can I answer it straight away: I had projects that were done within hours and I had projects of the same category that took days.
While empirically, there might be some correlations, we have (AFAIK) no study for that, so all we can offer is our own opinion. I would gladly share and compare mine with others, but I fear that's something beyond the scope of StackExchange.
