They’re still neutron stars though. As far as we know the only ways for a neutron star to stop being a neutron star is for enough stuff to fall into them that they collapse into a black hole, two merge to become a black hole, or if they get eaten by a black hole. Otherwise neutron stars are just about the most stable things in the universe.

Interestingly enough, the inner Layers of a neutron star are commonly modeled to have a temperature of 0K, since the extreme density prevents thermal movements