I have to disagree with you on this one, Elder. I do not appear to be unique in this area of "health" in TCC.
Michael appears to have had a similar eperience, for one.
I was intrigued by this topic, so I asked around about this a bit. I am close enough to two Wu family disciples to send them e-mail explaining this forum topic and asking for their experiences in this area.
They both experienced an increase, not a decrease, in levels of sexual desire and performance.
Also, these are two teaching disciples and they both went on to say that a lot of thier students have reported an increase in all around, oh... Let's say "vitality" over the years they have trained. No one has ever mentioned a decrease to either of them.
Not scientific in any way, but it does seem indicitave.
I can also tell you from personal experience that the opposite of what you seem to be experiencing is true. I taught TCC to beginners and intermediate students for a number of years, I have been told on many occasions by my former students that they too experienced an increase in all areas of health and even had a number of students, both male and female, report obliquely that their "vitality" had gone up quite a bit since they started training.
I remember this clearly, as it closely co-incided with my own experience.
Take these examples for what they're worth, but it seems to me the problem may not be with the practice of TCC or internal martial arts at all.
The age range I'm speaking about is between 18 and my best guess would be around 65. All experienced the same increase in these areas, so I don't think age had anything to do with it either.
I can't imagine why your experiences have been different.
If anyone knows, I'd sure love to hear the reason.