Doctor Who and Torchwood both do a lot with the idea of being either immortal or very long-lived--and, in a way, perpetually young. In Doctor Who, the Doctor outlives most of the people he knows, and is often shown having to deal with that. He's also telepathic, and very smart, although those two aren't dealt with quite as much. (Here, when I say 'perpetually young', I mostly mean his most recent incarnations--the earlier ones tended to be somewhat older-looking). In one episode his youth is actually suspended, and the 900-year-old Doctor is revealed to be, well, really, really, really old, as opposed to his current (at that point) youthful David Tennant form. He's also a compelling character, have I mentioned that yet? No? Well, he is.
In Torchwood, Captain Jack Harkness can't die. Or rather, he can--he just can't stay dead. He was originally a regular human from the 51st century, but something happened to him in an episode of Doctor Who and he can't stay dead anymore. He also barely ages--after over a century, he mentions that he's getting the odd gray hair. He spends the entire 20th century on Earth, waiting for the Doctor. Over that time, he fights in wars, he loses everyone due to wars, sickness, and old age, and he...well, he's very lonely. Not all the time, but a lot of it. He falls in love several times, is even married once, and each experience is different. They're also spoilers, so I won't tell you (even though there's every chance you know both of these fandoms already...) One of them actually says to him, 'Ten thousand years from now, you won't even remember me.' He's also occasionally shown dealing with cultural differences, but by the time Torchwood is actually set in, he's gotten used to a lot of things. Then again, he was also pretty much trained to blend in in different time periods for his former job, so that may have something to do with it.
And there ends my analysis of two TV shows you may have already seen.
If you want good and generally realistic handling of magic, try Tamora Pierce's books. If you want an especially good example of the responsibilities and years of study that actually come with being a powerful mage, try the Circle of Magic series (and its sequels) by the same author. Diana Wynne Jones' Chrestomanci series also does a good job of showing the responsibilities and dangers of magic, although they are technically aimed at slightly younger readers. If you don't mind that, though, I recommend them very, very highly. Other than that, there's something that's slipping my mind right now; if I remember it, I'll let you know.
(As to why I've included these: the Chrestomanci is a position held by a nine-lived enchanter. They're very rare, and very powerful. The series deals mostly with young nine-lived enchanters--in two different generations--being taught, well, responsibility, mostly. Tamora Pierce also has a tendency to write about unique magic users: Alanna is actually the chosen one of a goddess--which, believe me, is explored in depth--Daine is the strongest Wild Mage in...centuries, I think, and Kel--well, Kel doesn't actually have magic. She is the first openly female knight-contender in over a century, though. In the Circle books, Briar, Sandry, Tris, and Daja are extremely powerful at a young age, and use a type of magic that's often ignored or not even known about. The books focus a lot on the benefits, disadvantages, and responsibilities that come with their magic. ...this is all a lot more interesting than it sounds. Basically, Tamora Pierce is an amazing author, and she handles Sue-ish ideas so well I don't think I've ever even thought of accusing her characters of being Sues. In fact, the only character I've heard the fandom accuse of being slightly Sueish was Daine, and, well...I don't know. I like her. And the people who said she was Sueish meant it more in the way of 'Sue-like tendencies'. Not to mention that her world is still detailed and well-written. It's a matter of opinion, I suppose.)
Does that help? Or rather, is any of that what you were looking for, preferably in addition to being something you haven't read or watched already?
~DF