The Seebeck coefficient of a metal is expected to display a linear temperature dependence in the zero-temperature limit. To attain this regime, it is often necessary to cool the system well below 1 K. We put under scrutiny the magnitude of this term in different families of strongly interacting electronic systems. For a wide range of compounds (including heavy-fermion, organic and various oxide families) a remarkable correlation between this term and the electronic specific heat is found. We argue that a dimensionless ratio relating these two signatures of mass renormalization contains interesting information about the ground state of each system. The absolute value of this ratio remains close to unity in a wide range of strongly correlated electron systems.