Rapidly decaying oscillations of the thermal emission detected in the decay phase of solar and stellar flares are usually interpreted as standing or sloshing (reflecting) slow magnetoacoustic oscillations. We determine the scalings of the oscillation periods, damping times, and amplitudes with the temperature, considering both standing and sloshing oscillations detected with different instruments. In addition, the time evolution of different spatial harmonics of a sloshing oscillation is considered. Parameters of slow oscillations observed in the EUV, X-ray, and microwave bands, and published in the literature, are used. The damping time of slow oscillations is found to scale almost linearly with the oscillation period, as the period to 0.87 0.1, giving the average Q-factor determined as the ratio of the damping time to the period, of about 1. The Q-factor is found to scale with the relative amplitude to the power of with 95% confidence. The amplitudes of different spatial harmonics forming a sloshing pulse show similar time evolution, suggesting that the period-dependent dissipation is counteracted by another mechanism. The results obtained indicate that the damping of slow oscillations depends on the oscillation amplitude, and that the competition of nonlinear and dissipative effects could allow for the existence of wave pulses of a sustained shape.