i believe in acclimatization..
i spent 6 months in greece a couple of years back
and all i did was over time spend more and more hours in the sun...
i am a high risk person as well because i am covered in hundreds of moles (those brown skin spots not the animals

)
i got slightly burnt a couple of times but all i did was spend 3 days covered up and out of the sun until the red turned to brown
i got to greece in may and by august i could spend all day out in the intense sun without burning at all, and i was the brownest i've ever been...seems to have left me permanently darker...
anyway i go to a special 'mole doctor' to have my skin checked every 6-12 months and she said suncream was advisable but the next best thing was acclimatizing...
now this was in the mediterranean but however i hear in australia and southern america, ie. the far south of chile/argentina, because of the ozone hole/thinness, the sun will nuke you and kill you unless you wear protection...
um i am a great believer in balance, so a bit of both always helps, but i also think very fair skinned white people are at risk, unless they go through a long period of acclimatization, so i reckon cream is useful for them..
i started off really white when i was young but i've spent so many years in the sun recently that now i have a permanent tan..