We report on the delayed statistical electron emission of photoexcited fullerene anions C_n− (n=60, 70, 78, 84, 90). Kinetic energy release distributions have been measured by a velocity-map imaging spectrometer for delays of about 100 ns after the nanosecond laser excitation. They show significant variations as a function of the molecular size. Their analysis in the frame of the detailed balance requires the description of the reverse process, namely the electron attachment to the neutral fullerene. For this purpose, the quantum Vogt and Wannier's formalism is used, which allows introducing an empirical expression for the intramolecular vibrational redistribution (IVR). Information on the IVR has been deduced from the fit of the experimental spectra and has been interpreted using the molecular symmetries. In particular C₆₀ has an original behavior related to its icosahedral symmetry.