High-purity fused silicas (800-1000 ppm OH) have been studied by in situ Raman scattering in the 1000 degrees-1400 degrees C temperature range, with a particular interest on the behavior under long annealing cycles. We evidence for the first time the relaxation times of silicas in the vicinity of T(g) by direct monitoring on time-wavenumber 2D representations of the main broad band at 440 cm(-1). These relaxation times appear longer than expected through existing descriptions, and could serve as indicative needed annealing times for thermal treatments and changes of fictive temperature.