I started kegging 9 months ago and found it takes about 3 weeks for the beer to become well conditioned whether it is forced carbes or naturually carbed with corn sugar. If you force carb the beer will absorb the co2 faster if it is cold and may get the carb level you are after sooner but it may also still taste a little green, (or at least mine did when I tried to shorten the process to just one week). It will also depend on the size of your co2 source whether you want to force carb (which takes more co2) or carb with corn sugar and then place under serving pressure.
North Liberty, Iowa
"Beer will change the world. I don't know how, but it will."