Blackbody radius evolution over time. Top panel: evolution of the blackbody radius, overlaid with the best-fit linear expansion model (orange line). At late times the radius reaches approximately 5 × 10¹³ cm (but with large error bars), which corresponds to several hundred R_g for M_BH = 10⁶ M_⊙. Bottom panel: same evolution, but now converted to units of gravitational radius for two different black hole masses. The orange and red stars mark the inferred disk outer and inner radii, respectively (see Sect. 3.6). At late times, the blackbody radii overlap with the estimated accretion disk size (highlighted with the shaded area, assuming that the disk size has not changed significantly from the last epoch that can be modelled).