Where is the line between being a videogame and being a simulation?
With most of the "people" that pretty much lobby the importance of "immersion" and "realism", the word videogame is a cuss word. So if you ask someone who thinks rationally, you cross from game to simulation when you start to sacrifice playability and fun for immersion and realism.
With the idea of varying shop hours, it would have to cluster up, in other words, all the shops in one town open and close at the same time, but differ when you go from one town to the next. Otherwise, it becomes too chaotic for the player and would be a horrible idea.