Mine really started to be noticeable (even by others) around the 3 month mark. Even at almost a year on T I don't think I've completely dropped yet. I don't sound like the average 32 year old man. More like a young guy in his late teens/early 20's. It's a gradual thing, and like others have stated men's voices change over their lifetimes. 

Mine got deeper at about 2-3 months and again about 8 months. It hasn't really ever broken or anything but I got a hoarse voice.

--Jay