Maybe I'm wrong, but my hunch is that if average sun exposure were a dramatic factor in aesthetic perceptions of aging we would have seen equally dramatic evidence of the fact from people who have very little or no sunlight exposure - e.g. women in burqas, miners, night shift workers, prisoners etc. Also, parts of the body that are almost always well shielded from sunlight, like the buttocks and breasts, do definitely show obvious aesthetic signs of aging in many/most by fifty years of age or so.
But I've often noticed that people's faces show the most signs of ageing, followed by the arms. And in some Western women, the breasts (because of wearing low cut tops a lot).
I often see men in their 50s or older with strangely young-looking, wrinkle-free white legs. They have most likely exposed them to the sun only a few times a year. Compared to the wrinkled up face and arms, there's a clear difference.
Obviously in the 60s and 70s you'll usually see wrinkles everywhere, or if not wrinkles, perhaps sagginess. The loss of collagen or fat and the action of gravity means things droop, including the buttocks and skin around the arms and neck. I would say this is a sign of ageing that the sun doesn't play much of a role in, but up until the age of about 50, sun damage is probably the dominant factor in premature ageing, particularly on the face, neck and hands, which are exposed pretty much every day, even in winter.
