In fact, my experience with ceremonial circles is non-existent. I cannot contradict you here, as I am not knowledgeable enough on the subject. I agree that a lingering energy may still be present in the place of the working, but I believe this actually depends on the working your doing and on the banishing you're performing. I don't think it's either an open portal or nothing.
Again, I do not believe that each time one practices magic in a circle that is the same quality and amount of energy raised. Of course, continuous and powerful magic around a place / item in the long term will need to be managed properly.
I think you are missing an important point here. The places you mention were meant for public use, rituals would be performed almost daily. Possibly communities would gather around them. You need to keep a place like that open because it is always needed, it's unlikely the case with a private living room.
I don't find this arrogant, but I don't agree. Banishing entities who have been summoned is present in a lot of folk magic, at least where I come from. I also do not think that for each ritual you need a Stonehenge kind of experience. I think we are comparing two very different scales here, as of course a place where magic has supposedly been practiced for centuries will have a different kick to it than, again, my living room.
We have a great difference of opinion on what "Banishing" means. In my teachings banishing a thing is to destroy its earthly form and drive it back to whatever plain of existence it originates from. So its not something i'd do simply to do and at each event where I opened a conjuring / summoning circle. Yes many culture's utilize banishing just like many use exorcism's to drive out unwanted or possessive spirits but its not something that is done simply to do it. Especially in the content that anything at a ritual space has been called by the practitioner(s) either directly or by implied consent. Implied consent falling into the realm of using elemental's, land spirits, etc who may come themselves or send a avatar or lessor spirit in their place to determine what is needed. Figure the king is not going to come himself but send someone as his messenger, when dealing with daemons or demons the same pattern is often encountered as well.
You appear to be using banishing as I would use releasing. I would release the wards, glyphs or boundaries I have created to focus and direct any energy stored or raised for some action. Though the raising and storing of energy is where the vortex and creation of a hot spot comes into play. You can never fully release what you've created and any spell you've created that does send forth something remains in operation and continues from the spot, the object or even the tie that binds the practitioner to their sacred place. So your ritual / ceremony lasted lets say an hour the affects / effects of that last for what ever duration it takes to complete so its all tied back to where the point of origin is located though the stream moves forward and away from it. So even though like a dam is opened the water released and the dam then closed, the pathway and network remains connected for any future action. As such it can be followed back to its origin. In some ways the way you use banishing reminds me of some stuff I was taught within a Stregian content but that was in regards to things like the evil eye or other malicious workings.
I'd thank any greater entities I called or invited to participate in my usage. Figure an honoring ceremony you'd invite the gods / goddesses or greater / lessor entities you may have asked to be present. If I bound something through summoning or conjuring and forcing it to appear then i'd unbind it and release it but not banish it when that would mean to destroy its earthly form which would prevent it from doing as I have asked or commanded.
I had a person once use the comparison of a piece of swiss chesse for how we work. As practitioners we open a portal into a differing aspect of reality. Each of us as a group or individual open these portals and they sort of become tagged to us. Yet once done we can't fill it back it, we can cover it over, we can't do anything except to guard the portal entrance we created and opened. So we devise objects that represent the theory of that portal opening to us and bring them together or separate them in the hopes if controls the portal or space we've created. Sort of building a safe house over top of it and. If we use many objects then we have it spread apart and the actual opening is smaller. Yet if we draw it upon an item and use that item as the opening portal it stays the same size and the portal opening in fact moves with it. Again we are bridging into a place that is not of this dimension or reality so it is not really bound to the limitations of this reality.
Sort of a side line note but the person also presented a really interesting argument that the origin of the flying carpet aligns to personal carpets being used as magical portals. Create the design in the weaving or drawn upon the carpet itself. Sit upon the carpet and you "Fly" to where ever or when ever you wish to go. Then when done you roll the carpet up, store it away and wait until needed again. But you place a magical safe word on the carpet so it can not be opened by chance or anyone else and have access to your flying carpet. So to the person on the carpet when, where or what they see and do matches many of the stories that come down. Then the elements that get passed into the folk lore speak of the magical carpet that the person flies upon to visit so many places.
But the portal itself is always open. Always something coming through though in most instances we try to narrow it down to a fine trickle of energy and use that energy to work our endeavors. Then like some miner with their vein of gold we guard and hide the mine less someone else gain access to it.
That same concept is found at the temples, shrines, sanctuaries, etc about the world. The public had access to the public areas where offerings, feasts, ceremonies, etc where held and performed. Yet they were not the heart, soul and power source of those places. Those were limited to only a couple of people who gained access to the innermost sacred places. The spots where the statuary and such to the god / goddess where housed and brought forth from and returned to when the ceremonies and such were done. So yes there is a sense of energy at the outer edges much like there is a sense of energy around most churches. Yet the energy and presence of it gets stronger as you near the altar where the Priestess, Priest, Pastor, Reverend, etc is ridden and channels their God, god or goddess and speak to the people. Basically one sits in the presence of their divinity and one is bathed and surrounded by the physical energy of their divinity. A great many practitioner's I've known don't like to compare their magical workings to the layout of a divine working though much of the symbology and material components are the same when a sacred space is created and a power vortex is opened. Me personally I think them the same the only difference being we tend to take the role of priest / priestess and make the energy do as we desire where the church uses the person as a figure head and prays in general in the hopes they can be heard.