Several characters in the pulps had permanent tans. Sir Denis Nayland Smith (despite living in England for years) kept the dark brown skin he had acquired in Burma. And the Man of Bronze himself, despite spending months at a time in the Arctic, still retained the copper color he got from “a thousand tropical suns.”
Is this possible? Can you tan so thoroughly that it never fades, even years later?
Not unless the radiation from the sun exposure reprogrammed ones genes to keep melanin production high.
Melanin breaks down at a constant rate. Only people genetically disposed to have dark skin (Africans, Indians, Australian Aboriginies [sp?]) produce it faster than it breaks down, thus appearing darker. Europeans, Asians, Inuit, etc. can stimulate their melanin production higher with UV exposure, but it will fall to genetically-decided levels once that exposure is lessened.
I know some people that at first glance have a “permanent” tan. But then I realized that it’s just their skins have become leathery and wrinkled from sun exposure. Since that doesn’t go away, the tan that isn’t there is kinda assumed.
(Their skin might be slightly darker due to structural damage from their tanning. But it’s not a real tan.)