The photoluminescence (PL) spectra of GaInNAs(Sb)/GaNAs quantum well samples emitting around 1.5 μm, annealed at different temperatures and for different durations, were compared. Two distinct processes with widely different temperature dependencies are identified: PL intensity improvement at the beginning of annealing and PL intensity degradation when overannealed. The degradation process has a much steeper temperature dependence than the improvement process, so lower-temperature, longer-duration annealings result in both a higher photoluminescence intensity and a broader process window than higher-temperature, shorter-duration annealings. The lowest threshold of 1.55 GaInNAs(Sb) lasers up to now was obtained exclusively with short, hot annealings, this finding offers another method of further improving dilute-nitride laser performance. Similar trends are found for different compositions and thicknesses of GaInNAs(Sb).