Board Thread:Questions and Answers/@comment-30272238-20161020193809

I get the impression that some don't, but most do and can't find where this is clearly stated. For example, Apophis and Pharaohs seem like they're eternally youthful based on their status and backgrounds. That monster girls have difficulty getting pregant, and thus a low reproductive rate, would suggest they're long if not eternally youthful. In the real world animals with long life spans tend to have lower fertility and fiction does tend to go with [|Immortal Procreation Clause].

On the other hand, that one explicit motivation for human women to become Witches is eternal youth implies that it is indeed normal for most monser girls to grow old and die.

My impression is that most monster girls in general are longer lived than humans and this trait is extended to husbands that become incubi, but they do eventually die of old age. I wouldn't be surprised though if monster girls age gracefully and retain beauty throughout their lives except perhaps when they are very near the end. (I seem to recall reading a fantasy novel where this was the case for elves. Elves generally reached adulthood at about the same rate as humans, but looked to be in their twenties or thirties, by human standards, throughout their long lives and only started appear elderly when they were within a decade or few of dying.)

That monster girls are long lived or occasionally immortal would also indicate that the Demon Lord's long term plans have even further problems because a long or immortal life span with low birth rates means that the issue that monster girls don't produce human sons is further compounded. There's the extinction event issue. It would be less of a problem if all monster girls had eternal youth. 