just as with fae and vampires, I imagine stars, or more accuratley angels, would likely not age as normal humans do. These are spiritual beings, unnaturally in possesion of corporeal forms, and therefore untethered to the rules of mammalian biology. When humans encounter angels in canonical texts they often experience an awe alloyed by fear. This is absolutely how I, having interacted with the Gargoyle, would describe their presence. Even as the memory frays at it's edges and thins to translucency, I can still feel the rippling of goose pimples, the hotness behind my ears, the dilation of my pupils at recalling the Gargoyle. I was very much in need of a shepherd at the time
"The third angel sounded his trumpet, and a great star, blazing like a torch, fell from the sky on a third of the rivers and on the springs of water— the name of the star is Wormwood. A third of the waters turned bitter, and many people died from the waters that had become bitter." Revelations 8:10-11
The Gargoyle made the Tonic, and we know that juniper berries were a key componant, thus it was likely a very "bitter" concoction. The text also specifies that "a third of the waters turned". I believe in the context of the Castle, this was likely an allusion to their Task: to convert 1/3 of earth's population into members of the Castle. The need for more tonic directly corrolates to how many Castle members there are drinking it, as the cult grows so then too would the amount of Tonic being produced.
"Avery Etidorpha Wormwood" is an alias that we know the Gargoyle used on a few occasions. Now it may seem naïve of me to claim that someone who openly uses the name "Wormwood" may also be the same biblical entity assocated with the herb, but I would argue that ignoring such a factor is counterintuitive to the eventual answering of the question; Who is the Gargoyle? They chose this alias and I think that means something. Maybe it just means wormwood is a well-loved ingredient in the botanical community, or maybe its an ode to one's past, a simple, secret nod to the exceptionally complicated role of an angel who fell to earth.