Girls, Can I wear a 20 inch or even longer pearl necklace with a round neckline that comes up high. ?

I know that when I have been shopping lately, most pearl necklaces are short (18 inches and shorter). It seems to me that when a top comes up high and round that the necklace should hang further down. Does the rule usually still apply or not? I have a formal gown for a semi formal dress for a semi formal event.

Girls, Can I wear a 20 inch or even longer pearl necklace with a round neckline that comes up high. ?
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