Period distributions of non-polar cataclysmic variables from SDSS I–IV (Inight et al. 2023b), the plate survey that is part of SDSS V (Inight et al. 2023a), the incomplete but volume-limited (300 pc) Gold sample (Inight et al. 2021), as well as the largely complete but small 150 pc sample (Pala et al. 2020). While both SDSS samples show a clear period gap in the range between 147 and 191 min, the volume-limited samples contain too few cataclysmic variables with periods exceeding ∼120 min to derive meaningful constraints concerning the period gap. This result illustrates that the SDSS samples are still significantly biased against cataclysmic variables with periods shorter than two hours.