Dr. Deiterich who used to be on the expert forum stated several months. I'd say anywhere between 3-6 months. They advise not to become pregnant until 6 months after ceasing ribavirin as a precautionary.
I’ve come across a better explanation before; this is from wiki:
The volume of distribution of ribavirin is large (2000 L/kg) and the length of time the drug is trapped varies greatly from tissue to tissue. The mean half-life for multiple doses in the body is about 12 days, but very long-term kinetics are dominated by the kinetics of RBCs (half-life 40 days). RBCs store ribavirin for the lifetime of the cells, releasing it into the body's systems when old cells are degraded in the spleen.
I think most of it is out of us relatively quickly, but the residual is dependent on erythrocyte (red cell) turnover; this takes roughly 90-100 days in healthy individuals, perhaps more quickly in those with hemolytic anemia.