The formal name for this process is called the “frequency following response”, where the human brain will literally “follow” a specific frequency/beat after being exposed to it for (usually) about 8 minutes.  Technically the definitive term “entrainment” does not exactly match the actual process of what is happening to your brain when listening to these audios, but its close enough, and the name has stuck now with these products becoming more popular and widely known.

it says the following: “Running a delta sleep session throughout the night is not recommended as it can interrupt the normal sleep cycle”. I’ve been looping pure delta isochronic tones for about 5 days now, and have had quality sleep. Should I continue looping delta or should I let the videos play out without looping them? Will it will harm my health to do loop delta while I sleep?

At the end of just two weeks of use (I was now into the Equisync II cds), I experienced for the first time ever, what my partner described as Nirvana. I experienced a complete dissolution of individual consciousness, felt at one with everything, and felt the deepest peace, love, and complete bliss I had ever, ever experienced in my life. Since you do all the research on this, you know what I’m describing. Unfortunately, language does not express it. I have never experienced mind altering drugs, but I recall watching a documentary of LSD research, and one of the subjects described the exact same “feelings” as I had when she had received a micro amount of LSD.
I later learned that a Nobel Prize-winning scientist, Ilya Prigogine, had developed a theoretical model regarding the evolution of complex systems (like the human mind) that described these quantum leaps in awareness and brain-power I was experiencing—to a “T”—and explained why they happened! I read everything I could get my hands on about his work.
The reason I am telling you this is to consider that it is critical for you to seek advice from sources that have wide-spreading experience with brainwave entrainment. Having personally used the technology for over 13 years, in combination with many other more ‘traditional’ methods such as yoga, meditation, visualizations, positive affirmations, NLP, etc., I believe that my personal experiences and the in-depth research I have conducted in order to make sure I approach this safely, can serve as a good starting point for you.
A crossover RCT of a single session of theta stimulation in four healthy adults reported no significant improvement in verbal fluency or attention associated with the intervention and a reduction in immediate recall. Controlled comparisons reported significant benefit from the intervention in all three outcomes measured. Six pre/post studies reported significant benefit from the intervention for 19 of 28 cognitive outcomes.

Until NeuralSync™, brainwave entrainment involved inferior linear, single or sequential protocols - such as binaural beats or isochronic tones - that were natively restricted in their ability to affect the natural complex dynamics of the brain. But now, NeuralSync™ significantly improves entrainment by incorporating EIGHT SEPARATE BUT SYNERGISTICALLY-INTERACTIVE DIMENSIONS into a dynamic and cohesive process powerful enough to compel the brain to produce whole-brain synchronization for intense effect. Incredibly superior to binaural beats or isochronic tones, NeuralSync offers an entrainment experience beyond anything you've used before.

The mechanism for this is that when your eyes or ears are exposed to a particular frequency of pulses or beats, the thalamus first distributes this information to the entire brain, including the visual and cerebral cortex where neural activity begins to synchronize to the incoming frequency, producing hemispheric synchronization and a balance of brainwave activity across the brain.

I just had to let you folks know how impressed I am with your Equisync CD’s, (Equisync I, Equisync II, & Equisync III). I just received the last two yesterday. I tried them both with amazing results. Especially the final CD, Equisync III. It creates a tone that is like a plane of sound that exists between the eyes all the way through your brain to the back of your head in the center. It is a tone, that if concentrated on purely, is the most amazing thing I have ever felt. I firmly believe it is some kind of door the the other side. It is like walking into a Lucid Dream. I am amazed many do not or know not about your technology and it’s wealth and value in understanding the self as well as our place in the Cosmos. I have recommended your product to others and will continue to do so. It is the first product, that has literally blown me away, and without the usual hype of products, such as these. It is it’s pureness, and it’s simplicity, that enables one to help oneself and others in this life. Using the CDs, at least initially, as almost entirely eradicated the intense pain I have felt for years. I have many forms of arthritis, all of which are degenerative, and incredibly intense. I have been able to work in my garden almost all day, without the usual restriction of pain and fatigue. I truly applaud you folks, you are definitely a Godsend….
Some research suggests that the benefits from brainwave entrainment can last a lot longer, and still be seen for some time after you've stopped using it.  Study participants have still maintained improved test scores a few weeks after the stimulation had ceased.  Research on the long-term benefits has so far been minimal though, so how long the effects last is still up for debate.
Hi Marko, that isn’t one of my videos you referred to, so I can’t really answer you properly as I don’t know how their track was created. For the best answer, you should really contact the video creator. There isn’t any research that I’ve seen to suggest that you could harm your health by looping a delta track. During a typical sleep cycle, your brainwave activity will usually go up and down between the delta and theta range. It may be that you won’t experience the same quality of sleep if you spend most of your time producing mainly delta activity. With my 8-hour sleep track, I fluctuate the frequency range to try and emulate a typical sleep cycle
Slower still are theta waves. Theta is best known as the brain wave state of dreaming sleep, but it is also associated with a number of other beneficial states, including increased creativity, some kinds of superlearning, increased memory abilities, visionary experiences, and what are called integrative experiences (where we make broadly-based positive changes in the way we see ourselves, others, or certain life situations).
Delta brainwaves have the slowest frequencies, ranging between 0.1 and 4 hertz, and these are the brainwave states associated with deep sleep, trance states, and unconsciousness. Few people can remain awake during delta brainwaves states, although this state is recorded in awake infants between ages of three months and one year and also in babies just before birth. Delta waves are also linked with increased production of HGH, DHEA, and the neuro-transmitter serotonin.
Jump up ^ Trost W. and Vuilleumier P., Rhythmic entrainment as a mechanism for emotion induction by music: a neurophysiological perspective. In The Emotional Power of Music: Multidisciplinary Perspectives on Musical Arousal, Expression, and Social Control, Cochrane T., Fantini B., and Scherer K. R., (Eds.), Oxford, UK: Oxford University Press; 2013, pp213–225.