Depending on your skin type, and how much time you spend under the sun. Sunscreens are effective only when you keep re-applying them every 2-3 hrs or so, not everybody is aware of this. I know of a lady who tans and doesn't burn, she hardly ever wears sunscreen unless going for a swim, is 35 but has a youthful complexion, no wrinkles at all.
I think wrinkles are bound to happen as a result of aging (lack of collagen) among other induced lifestyle factors like smoking, stress, etc. The age wrinkles start to appear varies for everyone. For my grandmother, it was around 50. For me, 33. She loves the sun, never bothered about sunscreen and now in her 90s she gets mistaken for a 65yo.
