Rarely =/= never. Like some arguing you can't quantify love. I argue you can't put an age on it.
- My mother knew my father all her life, started dating him at 17. Married him at 18, and is still with him at 52.
- UFC fighter Rose Namajunas has a controversial relationship with her fiance Pat Barry due to the age difference & how young she was at the start. She met him at 14 (he was 30) she started dating him at 16, and is now engaged to him at 26.
- Last I heard my former best friend was engaged to her first & only love. They lost their virginity together at 19 or so.
There's plenty of examples like this. Now just because it hasn't happened to you, and
I mean you generally not personally, doesn't mean it's nonexistent or unrealistic. Plenty of people have married their HS sweethearts & stayed with them.
When Buffy was in her 20's, she still admits her feelings for Angel as love. And as a young woman, she'd know. She's never said
"Well Angel was just a silly HS thing." Even in her late 20's, she's still stuck on Angel.
Plus Angel is an immortal adult who'd been around for over 200 years. He didn't have too much changing to do. He's a baked cookie for the most part. lol Buffy is the growing & changing one, and her feelings for Angel still haven't -even heading toward 30. In the comics, she was jealous of Dawn hugging Angel and pulled her away from him.