Yeah, the civilian economy can also cause you to spend a lot of time on it. As when you have several hundred colony ships, they can dump more population on a world than it can handle, so you have to keep switching the demand/supply around every 5 days or so.
Also, your civilians produce more colony ships and fewer freighters than you really want, because they will only build enough freighters to handle demand, but will endlessly build colony ships.
Building the civilian economy is sort of a cheat mode, as they can also provide FAR more fuel harvesters than you will need in the early and mid-game.
It basically means that if you would double your economy (at your tech level) every 15 or so years without the civilians, you can double it every 10 with them. Civilian economy means no wealth limits on production, and no manpower needs diverting to financial centers or fuel refineries, so the top production is higher too.