Wells don't take 5 years to complete, they take about half a year each.  Just like building a restaurant or a house or a school.  We build hundreds of those too, and collectively they take many years to build as well.

The point is that any particular resident doesn't have hundreds of wells within potentially bothersome range of their house.  There's not likely be to be more than a few at most.  Just like there's not likely to be more than a few restaurants, or a few schools, etc.