That's an interesting question. Since you don't have a uterus and therefore there is less risk being on estrogen only (and even less so on transdermal), it would seem this is something you could explore with a knowledgeable and progressive physician (I know...hard to find!). The more I read, the more I think I'm going to be on it forever. Perhaps there is some additional risk to that but we have to take our risks somewhere. I'd rather take my risk with something that restores the hormones in my body rather than something that creates new pathways to bone maintenance. Not that I'm opposed to that either if needed but I'd like to use those options minimally.
I've heard interviews with Dr Felice Gersh who is an integrative ob-gyn located in Irvine, CA. She is very knowledgeable about and very pro-HRT. I plan on seeing her to figure out whether my dosing is adequate and to determine a long-term plan. I'll report back on that (but could be awhile). Another doc who is well-versed on using HRT is Risa Kagen though unfortunately, she no longer sees patients. I believe she does consulting and research at this point. As a start, it might be worth looking up those two docs to read about their positions.