Long-term evolution of T_asc as a function of the number of orbital cycles since T_ref = 57897.027668 MJD. Red points are the values found by Jaodand et al. (2016), which deviate from the almost linearly increasing trend found in this work. Blue points are from Papitto et al. (2019), and lighter blue points are from Burtovoi et al. (2020). Triangles, associated in the legend with the different NICER observations, are from this work. The thick dashed line indicates our increasing roughly linear trend. The dotted gray line indicates the sinusoidal trend that is similar to the trend found in previous work (e.g., Jaodand et al. 2016; Papitto et al. 2019).