This might have already been covered, I don't have time to read the whole thread right now:
From Sage Advice Compendium (ver 2.2, the last update I have), Page 2:
Does the Trance trait allow an elf to finish a long rest in 4 hours?
If an elf meditates during a long rest (as described in the Trance trait), the elf finishes the rest after only 4 hours. A meditating elf otherwise follows all the rules for a long rest; only the duration is changed. [This answer has been altered as a result of a tweak to the rules for a long rest, which appears in newer printings of the Player’s Handbook.]
Every ruling is up to interpretation by the DM and group to decide on, but even with this alteration, we continue to stipulate Elves need 8 hours still to recover HP, features, spell slots, etc. as other races. But, that is just our group. Cheers.