Histogram showing the distribution of the number of erodays that all sources in the SEP field were observed for, in eRASS1, 2, and 3. The coloured in histogram depicts the distribution of the number of erodays of observation of variable sources. The grey dotted line depicts an inverse square relationship, which approximately matches the decrease in the number of sources observed at a particular logarithmic interval on the number of bins. We only counted bins with a fractional exposure larger than 0.1.