@Dr. Who And I'm not disagreeing with what you're saying (for the most part). However, that (Pfr to Pr) doesn't tell the whole story. There are various other metabolic processes that occur during lights out that a short burst of far red light cannot reproduce. It does not "shorten" your lights out period. Again, if that were true, then 8 hours (or less) of darkness would be ample to maintain bloom (w/far red exposure) as there are a number of documented "10 hours of dark" grows w/o far red. That, and greenhouse growers wouldn't have to utilize "covers" to initiate bloom due to the far red light that plants are exposed to. It would also indicate that those same plants would be able to bloom at any point of the year (at least, here in CA), as there isn't any period of darkness of fewer than 8 hours.
Far red doesn't put them "to sleep" either, the plants own internal clock does. I'm sure that you have noticed that they are "ready for sleep" moments before lights out (regardless of your schedule) and prepared for lights on moments prior. Lights are at full intensity up until the moment that they shut off, but the plants are "asleep" before this happens. Don't need a lab coat and peer reviewed work to recognize that. This, indipendent of far red exposure (if any).
Not arguing, just pointing out that "It isn't as simple as THAT".