Mild sunburn usually lasts 3-5 days. Moderate or severe sunburn usually lasts at least several days longer. The effects of each episode of this radiation damage, however, are long lasting. Each sunburn increases the risk of early wrinkles, premature aging, senile skin lesions, and skin cancers.
How old does a song have to be to be considered a classic? In my opinion a new generation have to grow to adulthood for a song be regarded as a classic therefore somewhere between 20-25 years would di it.
In fact, for a classically trained musician, the term 'classical music' is a specific genre, typified by Mozart, and refers to music written roughly between 1750-1830 (though it's the style, not the date, that's important.)