How long should construction take?

I saw the discussion about how the time progression would go (hours vs days vs years, etc.). Of course, this all depends on whether construction should be a core facet of the game, but it occurs to me that one of the first things that would be noticed in CB in contrast to previous city-builders is that construction takes time.

In real life, as I understand it, a house takes a few months to build (let's say three), major roads and stores take a year, and major infrastructure projects and skyscrapers can take years up to a decade. When it comes to gameplay, this could have a major effect. Should we have buildings and roads be usable almost right after they're plopped? (as is the case in most major city building games) Or should we aim for a more realistic approach, where you draw up your plan for a bridge, but have to deal with traffic management for a few hours of gameplay before the shiny new structure comes online?

Personally, I'd advocate a middle-of-the-road approach, where houses and streets are usable within a couple minutes and major skyscrapers and highways take perhaps an hour or so of gameplay time. That way, you have to anticipate the delay and hassle of managing major construction projects, without it becoming a dominating factor that overwhelms everything else.