Ideally, you only need to leave the beer on temp control until you hit FG. Realistically, you really only need to leave a beer on temp control until the most active part of fermentation is complete. Slower, cooler fermentation towards the lower end of the yeast's optimum range is always going to be cleaner and better.
When I am really jacking up the pipeline, I typically keep a beer on temp control for about a week, then let it rest at room temp for about two more weeks before kegging. Once the most active part of fermentation is complete (i.e., no more airlock activity), you are not FULLY at FG most of the time, but the yeast are not going to put off any off flavors as they wax off those last few gravity points, so it's fine to finish up fermentation at room temp. Once you hit FG, bulk conditioning processes then start, where the yeast will start to eat alot of the leftover nutrients that sometime lead to off flavors. Obviously, this method would be a little different for higher gravity beers or styles that need to be consumed young, like wheat-based beers.
The one other thing is I always put a t-shirt over my carboy to make sure no light penetrates beer to introduce skunking while it's sitting in my back room.
As far as the slight temp swings, that's not really going to affect your beer either. There is enough thermal mass in five gallons of beer that the actual temp is not going to change hardly at all over the course of a few hours of temp change in your house.
Hope that helps!