Distribution of the exposure time of sources in the SEP field, for eRASS1, 2, and 3. This quantity describes the total time that a source was inside the field of view, and does not consider vignetting effects. The distribution of the total exposure time for the sources we identify as variables is also shown. The grey dotted line depicts an inverse square relationship, showing that the drop in the number of sources within a logarithmic interval on the total exposure time is dominated by the decrease in the solid angle at a decreasing angle from the SEP.