  We study the out-of-equilibrium fluctuation-dissipation (FD) relations in the
low temperature, finite time, physical aging regime of two simple models with
strong glass behaviour, the Fredrickson-Andersen model and the square-plaquette
interaction model. We explicitly show the existence of unique, waiting-time
independent dynamical FD relations. While in the Fredrickson-Andersen model the
FD theorem is obeyed at all times, the plaquette model displays piecewise
linear FD relations, similar to what is found in disordered mean-field models
and in simulations of supercooled liquids, and despite the fact that its static
properties are trivial. We discuss the wider implications of these results.
