Hi Tony, Yes, and your coming from a biological theoretical standpoint. As in, it could make sense.
Now from me. I have studied these animals for nearly forty years(yes I am very slow) and come to your same conclusion or possible conclusion, from results in the field.
There is very simple evidence of this. Its on various scales(pun intented), depending on species. For instance. We all know cornsnakes are very local specific. Every so many miles, theres a migration of colof and patter, I.E. miami corns, up to Pine barren corns. Nearly every town has a unique type of corn. If gene flow was consistant, they would all be alike, and they are not.
With kings, its nearly the same. Brooks became brooks because of lack of gene flow. Goini as well. Not because of gene flow.
And your very right, its all about time. The phenotypes change with the years. Genotypes are most likely very consistant, but not phenotype.
Back to the field, I study many groups of snakes and gilas. I can tell where they came from in my study area, by their color and pattern. They are a little bit different. Yes, only a little bit different.
What we see is, the snakes we study, perfer to mate with the same male and return to the exact same place to copulate. Sometimes they stay in the same place, sometimes they move away if that area cannot support the colony.
When times are tuff, they move out a little more, when food is available, they do not move at all. What we do see is, when times are very harsh, they simply die in their own area. We do not see mass exdous of snakes looking for food. We do find them starving or dead in their holes.
So what we see is a high percentage in inbreeding(why dna can tell family relationships) and zero degrees of outbreeding. But, that is again temporal as you said, many events can occur to support outbreeding or geneflow. For instance floods are most like the best example I know of. So yes, outbreeding may mainly occur in short brusts, where inbreeding(family groups) is a normal day to day method of choice.
Also we watch congregations, and when these groups die off, they are not replaced. That is that area goes vacant for many years, then a pair may take up residence, then their offspring will recolonize that area. this is with snakes.
With gilas, their young inhabit the same areas. We see the young move in and grow up where their parents are.
Of course, where I live, is an extreme example of lack of gene flow, as in the desert, habitat is very spotty. In other areas, a population may be many many times larger.
But because we see locale types across all areas that kingsnakes occur, it does suggest that inbreeding or colonies are very common.
About captivity, if these animals always performed in one manner, it would be easy to label them. For instance, we know getula consume other getula, we do know that. But we also find them in groups, you know, three or four under one tin or board. So why are they in this group and for how long. Of course, most simply state, they are there to mate. But why are they in these areas for many months? we see them together for almost half the year.
Here, pyros do occur in groups. They do colonize small areas, and do not occur in areas right next to them. As do thayeri. I have seen this, but I do not know about all kings.
Not bragging, just using my experince. After one tucson show, I took out a group of herpers, so were academic herpers from texas. I went to an area, and one asked about pyros, I said go over there. Whoops he did and found a pyro. Then they asked about willards, I said because of the heat, I know of one shady colony, we went there and found one. Then they asked about greenrats, and I said I will take you to a place. I did and right there was a green rat. Then they asked about coral snakes. I said I know of this area. As soon as we got there, we found a coral. hmmmmmmmm yes, that was lucky, but I did know where they lived. Recently I took a young man out, we drove all over heck and back, I walked him to a place and said, its hot out, listen for a rattle. THere are banded rocks here. Two minutes later, he heard a banded rock. We photographed it. Then we got back in the car and drove over hill and dale. Hiked up and down and then walked a few meters up a hill, I then asked him to listen for a willards, within minutes, he said, theres one here. There was a real pretty one. Then he said, man are we lucky. I then gave him a look and said LUCK, I drove here and there, walked here and there, then stopped and asked you to listen, there was no luck envolved.
With our rattlesnakes, we have been marking them for 18 years, we have four/five basic mini canyons, all NEXT to eachother. The areas between them are merely a few dozen yards. In all these years, we have never had one from one site, go to the other site. Not once, yet we recapture them within their colony over and over and over and over. In fact, about 50% of the animals we capture on any given day, are recaptures. Again, in 18 years.
With my gilas, I have the same type of situation, We have never had one move to another site. But we find the same individuals in the EXACT same place, for many many years, our first individual has not moved in 29 years. Hmmmmmmm and gilas have legs.
So again, this is what caused me to entertain the thought of groups, yes, we saw them.
So with that in mind, I tested them. I did because I am unique in that I am both a field herper and a keeper. So I had oppertunity to test these things out.
The results are easy, hatch and raise them together and you have no problems, except if you starve them. Raise them together and you have not problems, except if you starve them. Mix those groups and you have big problems, they eat eachother.
So we now ask better questions, what do the young do when they are hatched. If there was no social component, they would simply leave eachother. Yet that is not what they do. They hang out for several weeks and do not leave eachother at all. Then it gets sketchy, as its not easy to track hatchlings. And interference is lethal to them. But we do find pairs and groups of other hatchlings, every now and then.
In fact, we find that most of the pairings we find in nature are age matched. That is, its rare to find an old male with a young female or visa versa. IT occurs, but is rare. Most of the time the pairs look like littermates.
The problem with studying this is, if you radio tag them, it mucks them up, totally. If you pit tag them it mucks up a percentage of them. If you do not break their natural defenses, you will see repeated patterns of behavior. that is, it does not much them up.
Again, this is not theoretical, as its results from actual field observation. Of course we and anyone can question what is actually happening. And we question it all the time. Cheers
Sometimes I think the kid with two pet snakes has something that those of us with 50 to 200 lost a long time ago. 
