Sorry, I didn't mean to hijack your thread, it's just that this whole business of what happened with DES (and the fact that high doses of other artificial female hormones are still being given to pregnant women) gets me quite wound up!
Anyway, returning to your original question, my personal opinion (based on what I've seen the ladies in Gender Reasearch saying, and on what I know about synthetic hormones), is that going on spiro long term is a very bad idea. Spiro's primary function is to block mineralocorticoid receptors, and it's only commonsense that having a long term, heavy blockade of your mineralocorticoid receptors for no good reason is likely to cause problems.
In addition to its antimineralocorticoid action, spiro is also a progestin, which is a type of synthetic hormone that's well known for causing harmful side effects in transgender HRT. Even spiro's antiandrogenic effects aren't necessarily a good thing when carried on long term and to the point where your testosterone is driven to very low levels. In addition to estradiol and progesterone, women ordinarily do have some testosterone in their systems, it's needed to maintain muscular strength and a healthy sex drive.
In my opinion, the aim of any type of HRT should be to drive your blood levels of hormones as near as you can to those typically found in healthy people of your chosen gender who are in their late 20s or early 30s (after the pubertal hormone surge has passed, but while they're still near their peak physical condition). To me it makes sense to try to produce a state close to what's found in people in the prime of their lives, not when they're elderly or sick!
According to Rachel Fracon (who runs the Gender Research group):
"Over the past couple of months, we have presented dozens of pieces of research showing how common sense and basic facts of medical science strongly implicate Spironolactone use (and especially extended use over years) as likely related to depression, dysphoria, ADHD like symptoms, fatigue, insomnia, weight gain, adrenal exhaustion, thyroid dysfunction and metabolic difficulties. "
Apparently, if you take sufficient estradiol to raise your blood levels of up it to GG levels, that on its own will usually suppress your T down to GG levels, so an antiandrogen might not even be necessary at all (even without an orchi). The only reason antiandrogens have become a standard part of MTF transgender HRT is that doctors used to always prescribe premarin or ethinylestradiol as the estrogen, both of which are so toxic that the dose has to be kept quite low (too low to fully suppress T production on its own). Hence an antiandrogen was needed to further suppress T production down to GG levels.