Well, Eve, this aspect of transition is all new to me, so take my words as my just talking out loud with the possibility of drawing out the facts from those who are really in the know. I thank you for giving me your view.
I'm not sure what my normal T level was before starting NBE. I suspect it was still quite high as it has been going back to age 30 when I was last tested and found to be at the top of the normal male range for my age. For me, indications of a healthy T level were evident even at age 66. High libido, multiple nightly spontaneous erections, no loss of body hair, advanced male pattern baldness, good energy level, and last but not least raging gender dysphoria due to T toxicity.
Even after 4 months on PM, my total T was measured at 109 ng/dl, twice the top end of a natal female's normal range. I very much doubt that T production drops to female levels in most men that are closing in on the age of 70. Sure, there are those who do suffer from very low T, I doubt that I'm one of them.
The other factor for me is the prospect for continued good health and long life. Based on my current health status and my ancestral history, I could easily have another 20 years of healthy and active life ahead of me, not counting the life extending benefits of dropping my T to female levels by having my testes removed. I certainly would not want to risk my health by taking larger doses of E and anti-androgens than necessary over that length of time.
Why do an orchi instead of full SRS? Well, that is certainly a good question that should be carefully considered. Many do just that, but, I agree that a heterosexual transwoman would not be well advised to do the surgery in two steps if she could afford the full SRS immediately.
On the other hand, a lesbian transwoman (e.g., me) in a sexual relationship with a heterosexual female (e.g., my wife) might want to consider keeping her penis if doing so wouldn't negate the objectives of her transition as a whole, but would increase the chances of preserving the relationship indefinitely. I know it is a fictional work, but the experience of the two main characters in the novel
Trans-sister Radio caused my wife a lot of concern for exactly that reason.
Of course, that rationale would fly out the window if at some point my sexual orientation changed to straight, and I wanted to experience sexual intercourse with a man as would a natal female. I don't see that happening, but who knows what can happen on this crazy journey.
These are some of the ideas that I will discuss with my HRT advocate/counselor when I appear for my appointment in less than a month. I'm really getting impatient...LOL.
Clara