  The evaluation of the long term stability of a material requires the
estimation of its long-time dynamics. For amorphous materials such as
structural glasses, it has proven difficult to predict the long-time dynamics
starting from static measurements. Here we consider how long one needs to
monitor the dynamics of a structural glass to predict its long--time features.
We present a detailed characterization of the statistical features of the
single-particle intermittent motion of structural glasses, and show that
single--particle jumps are the irreversible events leading to the relaxation of
the system. This allows to evaluate the diffusion constant on the time--scale
of the jump duration, which is small and temperature independent, well before
the system enters the diffusive regime. The prediction is obtained by analyzing
the particle trajectories via a parameter-free algorithm.
