This is actually a very good idea. In the last 2 weeks of veg i lower the lightcycle gradually from 18/6 or 24/0 all the way down to 12/12. Thus, your plant kicks into flowering directly. If you'd switch directly to 12/12, you'd have to wait for some 1-2 weeks for the plant to adjust, being very stressed due to the sudden change in light.
This is actually a very good idea. In the last 2 weeks of veg i lower the lightcycle gradually from 18/6 or 24/0 all the way down to 12/12. Thus, your plant kicks into flowering directly. If you'd switch directly to 12/12, you'd have to wait for some 1-2 weeks for the plant to adjust, being very stressed due to the sudden change in light.