We present the analysis of a sample 136 bright Gamma-Ray Bursts detected by GBM up to more than 1 MeV, which were collected during the first 3 years of Fermi operations. We derive GRB durations in various energy bands up to 10 MeV in GBM and, when possible, up to 1 GeV in LAT, thus expanding the duration–energy relationship in the GRB light curves to high energies. Finally we compare our analysis with previous results. For several bursts we notice evidence of a possible cutoff or break in the duration–energy relation at higher energies and investigate this behaviour by relating it with the spectral properties of GRBs.