The world is riddled with thousand-year-old vampires. Okay, maybe not, but books are. You know what bothers me most about thousand-year-old vampires? Their uneven distribution along a chart plotting them by their ages. (I also dislike their repressive misogynistic and anti-Semitic worldviews—those thousand year-old vampires are jerks—but first, we’ll talk about their ages.)
There are many different types of immortality. Some immortals can’t be killed, and others can’t ever die, whereas others can die but they don’t age (like Tolkien’s elves). Some immortals have been around forever and will continue to be around forever, but I’m not going to talk about those brethren of Cthulhu. I’m going to talk about the immortals that are born, can die, but don’t age, ie. most elves and vampires.
Here’s a way of thinking about it. Imagine it’s the beginning of the year, and for every day that passes, a token with the date is thrown into a hat. Once a week, a name will be drawn from the hat and removed permanently. At the end of the year, the hat is emptied and the date-tokens examined. By the end of the year, there are going to be a lot more December tokens than January ones. Not only have the January tokens had more chances to be drawn, but in the first part of the year, the odds of pulling them were higher.
Now imagine that instead of tokens, you have elves or vampires or other immortals, and the date is their birth year. Instead of being removed from a hat, they are being killed in battle or getting staked by an angry villager. The end result: you’re going to have a lot more young immortals than old immortals.
But there’s more to it than that. If your immortals reproduce (either by having children, or by biting humans) instead of spawning on a set schedule, then this effect is going to be even more pronounced, because in the January years, there are fewer of them to go around biting or getting busy with other hot immortals.
Now, you say your December immortals (that is, the late born) are just less savvy. They get their numbers drawn more easily because they haven’t been around to know any better, but weren’t the January ones also young once? And experience is not the only thing that determines survival; as any war-veteran will tell you, survival has a lot to do with luck. No matter how smart, how wise, how old you are, sooner or later some California teenager with a sharpened broom handle is going to punch your ticket.
Why is it, then, that the vampires populating novels are so geriatric? Is 100 a magic number for undead heart-throbs? Because I hardly ever read about the vampires who are 37 and dating sweet young teens, or the ones who are 64 and still married to the human they met half a century before the story started.
If your immortals keep reproducing as fast as they always have, you are going to have a distribution chart that’s closer to a pyramid. If you imagine the distribution chart as closer to a human population chart (for most of history, that is. It’s leveled out now due to a declining birthrate), you’re not going to have birthdates evenly plotted along a line, you will have many immortals who have only been around for a little while and fewer older people. You can have fun with this as well. When did your immortals first appear on your continent? It could be that the oldest immortals are all of continent A’s race, whereas continent B only has immortals that are < x years old. Was there a war 480 years ago? You may have a dip and a boom in the immortals’ demographics.
I’m not saying you can’t have a vampire or an elf who has seen 679 winters, but if every immortal in your novel is ancient, it doesn’t have as much of a punch as if most of the immortals are younger. It’s like titles of royalty at the reenactment society: If everyone is a lord or a lady, and no one is a peasant, then suddenly it’s not that big of a deal to be a lord or a lady.
The other thing you have to think about when you write immortal characters is your grandpa. Think of your most cantankerous, ornery, mule-headed grandpa. Years do to people what they do to wine or vinegar: they tend to take whatever characteristics are present and concentrate them. An oaky wine will become even oakier. A thrifty guy might become a miser. That guy who was raised to believe that Polish people are stupid? He has a good chance of remaining bigoted all his life. Now imagine that instead of being 70 years old, your character is 700 years old. He or she might have clung on to some really odd ideas. He or she might be living in an attic with several dozen cats, ranting about Huguenots.
Don’t let this dissuade you from putting older immortals in your stories though. They have their place. People who live for too long have plenty of years to build up emotional baggage. They might get PTSD, mind-altering diseases, and have their hearts irredeemably broken several dozen times. If your character lives long enough, he or she can become emotionally damaged, and it will only take a few plot twists to push them over the edge. Since torturing characters is one of the most enjoyable parts of being an author, let the fun begin.*
*I’m not a statistician (liberal arts major) so I ran most of this by a friend of mine who is. If you’re into statistics, and you have more to add, or corrections, the comments field is your day to shine!