My breasts were sore from the point when buds grew, which was about 1.5 months into HRT.
They stayed sore and very sensitive for a few months as they grew, varying in intensity a little from time to time... That lasted maybe up until 5 months HRT where not even I could touch them.
After that, the pain started to settle, and instead of just hurting, the pain came and went through the days. Sometimes they would go days without pain, and sometimes days of pain now and then through the day. The extreme sensitivity which was there at the start is mostly gone though. Also, they rarely hurt at the same time... normally it's just one side or the other.
They're still growing slowly, so I assume the pain just accompanies growth.