Current cosmological data puts increasing pressure on models of dark energy in the freezing class , e.g .
early dark energy or those with equation of state w substantially different from -1 .
We investigate to what extent data will distinguish the thawing class of quintessence from a cosmological constant .
Since thawing dark energy deviates from w = -1 only at late times , we find that deviations 1 + w \lesssim 0.1 are difficult to see even with next generation measurements ; however , modest redshift drift data can improve the sensitivity by a factor of two .
Furthermore , technical naturalness prefers specific thawing models .