As someone who lives in a sunny Mediterranean country, there's nothing wrong with a few minutes' walk without sunscreen in the midday sun, but the hours of sunbathing (even with sunscreen) don't look very pleasant to me.
People's own feeling on how the sun feels on their skin without sunscreen might be a great indicator of how good it is for you and an individual. Most people don't pay much attention to that, I would guess, but as a person with fairly light complexion (German, French, English, Irish, + minor unknown other) that grew up in sunny northern New Mexico, I find that the direct sun on a summer day feels good for just 5-15 minutes, while on a cold winter day I enjoy it much longer.
I agree, that's what I go by as well. After a few minutes it becomes uncomfortable in the summer, and I look for shade. The only exception is when you're swimming in the sea, when you don't really feel the sun's rays.