This is my understanding and experience to date with Far Red...
I do not want to misdirect anyone... I am not a master gardener, plant biologist etc...
I am very knowledgeable about lighting and electricity, dad was a electrician and lighting engineer...
He nearly found out about my growing many years ago when he found a HPS lamp I had sitting around...
When I converted to LED at the start of this year I started with the white LED Flood lamps. I knew they lacked in the Deep and Far Red areas of the spectrum. This is why I purchased the Greenpower LEDs to enhance the red.
I did not know how much "Red" or type I needed, Philips was not going to give me a "lighting recipe" for pot. I guessed when I bought 4 white/deep red bulbs, 1 Far Red bulb, and 1 white/deep red/far red bulb.
If I could do it over I would have NOT bought the Far Red products I would have purchased just the White and Deep Red lamps.
The Far Red Bulb was about 10% of my overall lighting which was too much and caused plant stretching beyond what one experiences with HPS, I did not have enough Blue to balance the amount of FR in my set up.
I caused undesirable results with constant use in my set-up in the first two weeks of flowering. I stopped using the Far Red. I Possibly cause some other issues too as I have learned more.
I have learned from this forum and reading some journal articles that enhancing the Far Red of the spectrum can be used to manipulate plants. Currently I do not fully understand this science...
One technique is end of day lighting with Far Red and at the simple level is used to tell the plant it is the end of day and it may help speed flowering.
I am planning to do a re-wire of my cabinet so as to try End of Day Far Red treatments some time in the future. Due to the power of the bulb it will only need to be on for no more than 5 minutes.
I still have more study to do before I implement this...
Hope this helps with explaining my experience with Far Red