Characteristic timescales for cosmic-ray loss mechanisms for a reference model with R_disk = 0.5 kpc and a rotational velocity of 20 km s^-1 of the star-forming region. Shown are in particular the injection timescale of the cosmic rays, defined as the timescale for massive star formation, the adiabatic losses for a full and a thermally driven wind model, and the timescale for cosmic-ray diffusion and for synchrotron losses. The dominant loss mechanism in this regime is due to the full wind model, while cosmic-ray diffusion would imply a transition for lower star formation rates. Injection timescales longer than the characteristic timescales for losses may induce significant fluctuations in the nonthermal radio emission. We note that the cosmic-ray diffusion timescale implicitly assumes an observed frequency of 1 GHz, while higher-frequency observations may probe more energetic cosmic rays with shorter diffusion times.