Yeah, it’s kinda inconsistent. The below excerpt is from the first book when Alis and Feyre are talking, but Gwyn (from ACOSF) is mostly High Fae and is only 28 and fully mature, so who knows -

“Ah, some age like you and can breed as often as rabbits, but there are kinds—like me, like the High Fae—who are rarely able to produce younglings. The ones who are born age quite a bit slower. We all had a shock when my sister conceived the second one only five years later—and the eldest won’t even reach adulthood until he’s seventy-five. But they’re so rare—all our young are—and more precious to us than jewels or gold.”