I haven't had a spontaneous erection since I started, but my T has been nuked into the dirt for a long time. I think the trick is getting that to happen in order to see any substantial changes. Have your hormone levels ever been satisfactory (125+ E, <40 T) for any length of time? If so, how long? In my case, T has been suppressed for such a long time that I don't think my testes have it in em anymore to make T even if I went off of HRT. Maybe that's all you need, is a long period of time where T is suppressed?
Also, I wonder if going on a starter dose for a long period of time builds up a certain immunity to the hormones ability to do their part in the future? Maybe if the body isn't initially flooded with E and T is not immediately suppressed, the body learns better how to metabolise excess estradiol and keep it from receptors in the testicles, therefore reducing the ease in which total suppression can occur.
We need more studies