Broadly, my understanding is that a major change in skin tone is 'worth' about 15 SPF, so tanning would fall somewhere below that. For a fixed amount of sun ex

Broadly, my understanding is that a major change in skin tone is 'worth' about 15 SPF, so tanning would fall somewhere below that. For a fixed amount of sun exposure, spreading out the duration is better both to establish a tan and to allow more time for skin recovery. But there isn't really a case where tanning increases safety, because you get the tan via exposure. It's like saying pilots who practice a lot are safer; for any given flight it might be true, but cumulative risk can only rise.