Lower Realm Demon Growth Notes
Starting from birth, Demons have a longer gestation period than humans, likely owing to additional elements like wings and tail, and although birth is similar to humans (it comes out of the same place), demon babies are born with their amniotic sac intact, it is also much thicker than a human amniotic sac, it is gelatinous, smooth, and multiple mm thick. Demoness hips have a more detached/deformable structure than humans for this reason. During the pregnancy, Demon mothers have a level of empathic and telepathic connection with their unborn child or children, although this does not start immediately after conception. Some months into a demonic pregnancy, it varies for each individual case, the expecting mother will wake up uncomfortable and terribly sick. She will experience random emotional fits intensely in the days and weeks following, as her infant becomes conscious, growing and struggling to understand what it is, where it is, what is it feeling, etc. This tends to smooth out after a while, as the soul within the child eventually comes to accept its new housing. Basically you could say that there are a lot of similarities to human pregnancies. In the latter half of gestation for demons, they can sense their newborns emotions fairly well, as well as their comfort or lack thereof.
Gestation takes 11-14 months and birth is a laborious, painful endeavor. After birth, traditionally they wait for the infant to pierce the sac and break out themselves with either the bony wingtips or if they have it, sharp tailtip. Some do not have these features, since tail shapes and the presence of wings varies among demon species. At infancy, their horns won't have grown in enough to be useful for breaking out, either. So in those cases after allowing the mother to rest a bit she will assist the infant in breaking the sac.
Once born, Demon children develop rather quickly for the first decade of their life. At 10 years old, they would be comparable to a 12-14 year old human child in height and physical development, but they would far surpass that in mental development. Demonic children are born with telepathic abilities, so they can express simple concepts like "hungry" or "sleepy" from the get go. Having this instant avenue of communication allows them to mentally develop much faster than human children, who have to learn to speak, read, write, interpret body language, etc. By age 15 a Demonic child will be finished with their schooling completely, and legally they will have their adult rights at that point. Many choose to pursue apprenticeships, or simply throw themselves into study for their favored topics for some years. Although they are adults at 15, many Demon youths do not move out of their parents homes until their mid 20's or even later. Sometimes they just hang around forever until they get hitched. At around 20 years of age, the physical body development will all but halt. This is because on the astral, everything is energy- so once your energy stabilizes, it's gonna stay the same. Essentially, they only visually age if they allow their mind, and their energy, to mentally age.
This is also part of why you can see Demonics and other astral beings who's outward appearances do not match at all the age that they are. Because their outward appearance mirrors the "age" of their energy. Just like Humans.... some Demons never mentally grow up.
Despite being technically adults at a younger age than we are, Demons tend to be rather emotionally volatile until around 150~ years of age for standard Lower Realm Demons. For some it takes a lot longer. This is typically due to self exploration and having successive crisis's of self where they try to seek purpose in life and go through mood swings, then after like 150 years they settle down.
Since everything is energy and they can live as long as they can find new energy to replace the energy they consume by existing, their lifespans are technically unlimited. However, most fall into an energy depression, and eventually die, around 20,000 years of age. There are exceptions, many, and some notable, but if you just grab a demon off the street, that's how long they will live on average.