There are several different aspects; I'll touch on a couple:
I think it will depend on the situation. Healing frequencies are normally about entrainment applying a frequency so that the bodily system will come back into a better synchronisation; like tuning an engine of a car.
If you are very sick then frequencies which bring systems back into more correct working order are good to run long-term. Consider the helmet that Novacure have developed for recurrent GBM sufferers - the frequencies applied stop the cancer from multiplying. On the other hand; ideally one wants to return back to health and then to be able to discard the machine; a best solution is not to be dependent on a machine so as to function.
Another point is that many of the so-called healing sets contain frequencies which are not necessarily healing; eg. 727.5 Hz is in some healing sets and yet it is targeting Staph (killing). => check out what Hz you are using.
There are some sets that have been developed here such as in 'songs of spine', 'kundalini', 'schumann resonator' that do fall into the category of immune-supporting/boosting/self-healing and are beneficial to run longer term;
usually via the remote.
The way frequencies applied should also be considered; sitting in front of a plasma bulb may have side-effects; as may running remote programs for too long. Depending on the situation, a little each day consistently, may work a lot better than a longer exposure occasionally. Healing sets can take ~3 months or more before you would see the benefit. Its similar approach to vitamins, minerals, breathing - it is what you do consistently each day (habit) that really are responsible for "miracles".
In the case of plasma and healing, my thought is that you should be limiting any specific frequency to at most 1hr day, (or few days week), and this should be built up over time. eg. Lymph drainage, Kidney normalize etc.
You should also look as frequencies as only part of the solution; probiotics, vitamins etc., plenty of water, green juices, plenty of sleep, meditation few mins every day also helpful.
Since this is realm of experimentation you should go with how you feel; it is easy to do too much. eg. If I run remote on myself for two weeks I find that it does start to irritate me; and give headiness, tightness around the temple etc.
Other people experience nausea. As I said on another post I don't consider this as herxing, or particularly beneficial, it seems to me it is just a sign you need to stop or change what you are running.
Sorry, not to give any concrete answer.
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