X-ray observations of quiescent X-ray binaries have the potential to provide insight into the structure and the composition of neutron stars .
EXO 0748–676 had been actively accreting for over 24 yr before its outburst ceased in late 2008 .
Subsequent X-ray monitoring revealed a gradual decay of the quiescent thermal emission that can be attributed to cooling of the accretion-heated neutron star crust .
In this work , we report on new Chandra and Swift observations that extend the quiescent monitoring to \simeq 5 yr post-outburst .
We find that the neutron star temperature remained at \simeq 117 eV between 2009 and 2011 , but had decreased to \simeq 110 eV in 2013 .
This suggests that the crust has not fully cooled yet , which is supported by the lower temperature ( \simeq 95 eV ) measured \simeq 4 yr prior to the accretion phase in 1980 .
Comparing the data to thermal evolution simulations reveals that the apparent lack of cooling between 2009 and 2011 could possibly be a signature of convection driven by phase separation of light and heavy nuclei in the outer layers of the neutron star .