3-4 weeks very far from harvest. 99% brown pistils is dead ass 200 years in human years, you can harvest from 60% brown pistils, everything else is not worth. Just start a new growth, gives you more over time.
You will recognize you plant slowing down in drinking and growth, then she starting to mature and its 1-2weeks to harvest. But i bet there will be atleast 2 more waves of pistils shooting out your plant, so buds will grow a lot. They also should, right now they pretty small.