Vertically integrated thermal timescales t_th,int (faded lower curves), front propagation timescales t_fp (solid upper curves), and viscous timescales t_vis (dashed–dotted curves, shown for the two sources with repeating CL events, Mkn 590 and Mkn 1018), as a function of disk radius for the five CLAGN in our sample given by different colors and markers. Horizontal dashed lines mark the empirically observed transition duration, and the solid dots indicate the radius at which t_fp matches t_obs. The magenta horizontal line marks the ∼30 yr recurrence period of the repeating sources; the star indicates the radius, R ≈ 29 R_Schw, at which t_vis matches it.