When I e-mailed Dr. Newman about this question, he said that it would be best to stay on it at least until the baby is getting most of their nutrition from solid foods. So at least a year. He said you could try weaning at that point.
The last time I weaned down from 120mg to 90 mg at 11 months. I didn't totally wean off the dom until I weaned my daughter at 18 months. I did stop taking the fenugreek around 12 months.
Jennifer