Oofta
Legend
According to the sage advice an elf can get a long rest in 4 hours but must otherwise satisfy all requirements of a long rest.  The base rules include 6 hours of sleep and no more than 2 hours of light activity which includes "standing watch".  
All elven trance does is reduce the 6 hours of sleep to 4 hours of trance. They still need 4 hours of not standing watch.
				
			All elven trance does is reduce the 6 hours of sleep to 4 hours of trance. They still need 4 hours of not standing watch.