Temporal evolution of the fractional area covered by hot pixels with respect to the whole image zone. The solid line represents hot pixels delivering more than 250 e⁻ pxl^-1 s^-1, while the dashed line corresponds to warm pixels delivering from 50 to 250 e⁻ pxl^-1 s^-1. Note the two sudden drops in the otherwise gradual growth of the number of hotter pixels. They occur in mid-June 2011 and mid-June 2012, when 2−3 day bakeouts took place.