What clinical factors do you use to determine timing of on-demand dosing of rituximab in ANCA vasculitis maintenance therapy?

I tend to use scheduled dosing (q 6 months) with RTX for maintenance in my GPA/MPA patients, but will occasionally use "on-demand" dosing in those who are eager to minimize their RTX, do not tolerate the infusions well, or occasionally those who have lower risks of flare (mild disease, no history of...