It's convincing to see how consistent all the castration data is, so I was quite surprised when the other day I happened to start reading A History of Life-Extensionism which was just posted online and I learned that one of the reasons for the early medical interest in sex hormones and hormonal treatment for health & life extension was because eunuchs were seen as short-lived, feeble, and stupid and since this was due to a lack of sex hormones, perhaps aging itself is due to a lack (emphasis added):

Brown-Séquard was a foremost authority in endocrinology, having proven specific effects of internal secretions, particularly those of the sex glands. In the widely publicized presentation to the French Biological Society of June 1, 1889, entitled the “Effects in man of subcutaneous injections of freshly prepared liquid from guinea pig and dog testes,”xciv] [[paper] Brown-Séquard announced his first attempts at hormone replacement therapy for rejuvenation, introducing longevity and rejuvenation research as an integral part of scientific discourse, and in fact establishing the field of therapeutic endocrinology.

In that seminal address of 1889,[xcv] Brown-Séquard proceeded from the observation that “true eunuchs are remarkable in their feebleness and their deficit in physical and intellectual activity” and the conviction that “analogous defects are observed in men who abuse coitus or masturbate” to the assumption that “these along with numerous other facts, clearly show that the testicles furnish to the blood, … principles which give energy to the nervous system and probably also to the muscles.” It followed that the supplementation of these deficits by animal sex gland extracts can retard senility. Their almost miraculous reinvigorating effects on his own person were described by Brown-Séquard, ending with a call for further research. (For Brown-Séquard the reinvigoration was not lasting, he died 5 years later, at the age of 77.)

...Perhaps the most ardent follower of Brown-Séquard was Serge (Samuel) Abramovich Voronoff. Born in 1866 near Voronezh, Russia, a son of a wealthy Jewish manufacturer, he immigrated to Paris in 1884 at the age of 18 and became a naturalized French citizen in 1895. (The drive and ability to adapt in the new country must have been strong, as Voronoff was often said to have become “more French than the French.”[cv]) In Rejuvenation by Grafting (1925),[cvi] Voronoff related the history of his method. While serving as a personal physician of the Egyptian viceroy Abbas II, in 1898 he observed the enfeeblement of eunuchs, which led him to believe in the invigorating and rejuvenating power of the sex glands. In 1913, he began experimenting with tissue grafting

(Stambler mentions in the footnotes Hamilton & Mestler's paper as a counterexample, but not the others.)

This makes me wonder how they could have been so wrong, if all subsequent data indicated long life for eunuchs. I tried to look up Voronoff's Rejuvenation by Grafting & How to restore youth and live longer but they are unavailable online despite existing in Google Books (gee, thanks copyright laws); googling snippets and in other books, quotes indicate he attended the deathbeds of a number of youngish Egyptian eunuchs and far from knowing any centenarian eunuchs much less several like the Koreans, says "I have never known an eunuch to exceed the age of sixty.", describing them as (quoted in Bourke's What it Means to be Human: Reflections from 1791 to the Present)

Voronoff encouraged physiologists to scrutinize the bodies of male eunuchs who could not be classed as 'truly men'. In a visit to Cairo in 1898, Voronoff was 'immensely struck' by the appearance of these eunuchs. They were

long in the leg, with small craniums and smooth, hairless faces. In the majority of instances they are obese, with pendulous cheeks, developed breasts, and enlarged pelves. They look, in fact, like old women, and the resemblance is enhanced by their characteristic high-pitched voices. The muscles are flabby, the walk and movements lethargic, the gums and sclerotics [white of the eye] pallid. They present, in short, all the signs so characteristic of the anaemic, feeble, and flabby organism.

Further evidence for their lack of manly characteristics included their 'slow' intelligence and lack of 'courage and enterprise'.

A Brief History of Bad Medicine implies that these were true eunuchs in the sense that they never experienced puberty and so should have had the maximal benefit:

...had the opportunity to examine some eunuchs - men who had been deliberately castrated at the age of six or seven...Fascinated, Voronoff took the opportunity to examine a large number of eunuchs and affirmed that these characteristics were common to them all. Quite reasonably, he concluded that all these effects were connected with the absence of the testicles...

I have no particular reason to disbelieve Voronoff, and it sounds very much like there was no apparent longevity benefit. So I wonder what the reason for the discrepancy between the modern data and the Asian & Ottoman data, and the Egyptian eunuchs? The main proposed mechanism, better immune system functioning, sounds as if it should give much larger benefits in Egypt than elsewhere, since as part of Africa there are so many infectious diseases there like malaria.