My body hair is mostly invisible now, way sparser and thinner than it used to be. You can only see it when the sun catches it right or when I have a tan, and I could honestly get away with not shaving my legs.
Timeframe-wise, I realized it had become super thin about a year into HRT? I think it's still thinning even now 2.5 years after that. I have heard that some people have less luck with it though.