@imnotasnowflakeElf trance: does it affect long rest for Elves? How? Just less sleep? A long rest is 8 hours for an elf, but the elf can spend much of it on watch and doing light activity, while others sleep.

— Jeremy Crawford (@JeremyECrawford) November 12, 2014

@GrogSDWhy does it say 4hr = “you gain same benefit that a human does from 8hr” when a rest is 8 hr of sleep.
A long rest can be a mix of sleep and light activity.

— Jeremy Crawford (@JeremyECrawford) August 13, 2015