Both my nipples were pierced at least 2 yrs preHRT - they were pierced at different times.
The left side (full hoop ring, titanium) healed perfectly without issues. Since HRT, no issues (but really only minimal breast development).
The right side (first an anodized horseshoe, replaced with my current titanium barbell) has always been abit problematic. From the start, the healing wasn't entirely perfect - alittle crusty discharge - but it was/has never really been overtly inflamed, red, tender, warm, etc. It got better after switching to the titanium barbell (the discharge stopped) and I figured it was officially healed. A few months after starting HRT, it has started to discharge again, but still, no overt inflammation, pain, tenderness, redness etc. Again - I've really only had minor breast development, but maybe the combination of this ring's placement (alittle deeper into the areola; the left side is abit more superficial, just at the base of the nipple) plus even just that minor glandular tissue is enough to start causing some irritation again. Of course, I do wear tight shirts (cycling jerseys, tight undershirts, sports bras) so that may contribute.
I do vacillate between removing the right side and starting over; I'm fairly certain the hole will close up, and maybe I can just get repierced through the scar tissue (or maybe slightly above the scar tissue). I personally love when you can see someone's piercings under their top, which is why I'm so resistant to taking the right side out.