Rituxan has a 3 month half life and would be out of your system on month 4. This is likely why you were advised to repeat the treatment.
Rituximab is a slow, steady, and thorough treatment where the immune cells that exhibit a CD-20 signature (the bad guys lol) are marked for Lymphocytes (T-cells and NK-cells) to take out (like in assassinate). It worked for me!
However, a rapid onset of CIDP symptoms and worsening conditions are best treated (in my opinion and based on my experiences with the disease) first with 3-4 days of Plasma Exchange, followed by 8-10 days of IVIg or SCIg. Sometimes an immunosuppressant drug may be needed to help the treatment to work. After this regimen ends, treatment with Rituximab can begin.
It should be noted that PE will cancel out IVIg/SCIg and Rituximab. Ig will cancel the effects of PE and seriously reduce the benefit of Rituxan. So the order of treatments would be important for the best results.