Summer dwellings are part of the transhumance round of pastoral communities. We call those buildings sheilings.
Basically here folks, couple of elders and a lot of the teenagers, took the animals to the Summer grazings....and they milked the animals, made butter, cheese, etc., for Winter up there. In some areas the shearing was done up there too, especially if they moved before the warmth really came in.
Family from the lower lands would come and go through the Summer. Folks weren't cut off, it was just part of the seasonal round, part of the wider agricultural economy.
Harvest time lower down and when labour was needed, the people moved as necessary. Actively engaged in the seasonal round.
Summer grazing on lands that were too harsh to live comfortably on through the winter, took the stress off the better grazings. That meant that the lower grasslands could be cut to provide hay too, but also that crops could be grown without constant grazing from livestock.
Moving the animals, cattle, sheep, goats, even geese and ducks, gave the lowlands a chance to recover, cut down on the mud !
Older people who grew up with this kind of farming spoke of how much they looked forward to the shifts, the company, even the work. There was a lot of pride in making good of it. Healthy fattened up animals, good cheese, etc., It was exciting, like us going on holiday I suppose, but it was a long holiday, and they were young and fit and they had fun
In other areas, the Alps, Himalayas, etc., I don't know if there were quite so many people moving about as there were here; I think they had to walk further, drive the beasts longer than a couple of days or so, but here you can see the higher grounds that your family traditionally grazed, and people did move back and forth.
I'm sorry, I don't know the links for the Welsh examples....maybe John Fenna might ?
@John Fenna
but some relevant readings...and they're interesting too I think
scarf.scot