For the most part yes, but there are better ways to time it based on the plant's priorities. For instance in the last week or 2 of plant flowering, the plant focuses less on stretching and more on resin production. This is why for the last week or 2 of flowering, many people like to switch their HPS for Metal Halide. Yield is reduced only slightly but resin production is increased by a good deal. In general, it's good to use both blue and red spectrum lights, but you always want to emphasize a spectrum at a time the plant uses it the most, rather than in a set proportion.