Have to disagree with the cfl for 18 hrs being better than sunlight + cfl to make up the hours.

This is how I veg year round and how I flower through winter, the best of the natural light with an indoor top up to make up the appropriate schedule. It really isn't difficult if your life allows you to be home every morning and evening to move plants around and you live at a favorable latitude.

Neither is it a problem if a vegging plant sees dusk fall outside before it comes in for a top up, happens regularly around here. A flowering plant needs more care to maintain light cycles, but again, it really isn't that hard.