How do you decide when to extend rituximab redosing beyond a 6 month interval for replasing multiple sclerosis?

In light of the published study, the discussion that I've had with patients revolves around utilizing CD19/CD20 counts to guide infusion frequency.

I start discussing extending the dosing interval after the first year on rituximab, but rather than at set 12-month intervals, I also use B-cell repopulation (CD19 counts) as a guide.