Wolverine will outlive us all, and I don't mean that just because he's fictional; the character has been shown to die, multiple times, and always comes back to life, and many stories have been written about a future Wolverine who's outlived all his friends and still keeps going (Onesuch is still ongoing; Mark Millar and Steve McNiven's "Old Man Logan," which is best described as "They've seen The Unforgiven and Mad Max and wanted to put them together with superheroes." It's still running in the regular Wolverine comic).
Not everyone is happy about that; Marvel editor Tom Brevoort, who edits the character in New Avengers every month, complained about it recently in his official Marvel blog:
It seems like, over the last decade ago, we've pumped the nasty little guy up to such a degree that he can regenerate his entire body after it's been disintegrated by a nuclear blast. We've seen him torn in half, cut his head off, and still he just keeps on ticking. And that's just in books I read this past weekend.
At a certain point, I have to wonder: where's the drama anymore?
Remember when a dozen ninjas with swords were a legitimate threat to Wolverine? But if the guy can reconstitute himself from a single atom, how is such a fight anything other than a foregone conclusion?
At first, Wolverine's resurrections came with special conditions. He died and was resurrected from a single drop of blood in 1987, but there was a cosmic crystal that could grant wishes involved. He died and was resurrected again a year later, along with the rest of the X-Men, but this time a magical goddess was around to bring them all back as a thank you for saving the universe. That kind of thing. But as time went on, the character just kept dying and coming back - whether it was voodoo-esque resurrections by shadowy assassin organizations or his body healing itself after amazingly powerful explosions - and by 2007, someone needed to explain just how he kept managing to pull it off.
The explanation came in the 2007 storyline "Logan Dies," collected in the 2008 book The Death of Wolverine (a book described thusly: "The arc is the dumbest thing I've read recently. So dumb that a simple plot summary also serves as a damning review"). The basic plot is this: Back in WWI, Wolverine happened to meet, fight and defeat a mysterious being called Lazaer. Turns out, though, that Lazaer was actually an angel of death called Azrael - Yes, the old "Johnny Alucard" trick - and as a result of this skirmish, everytime Wolverine dies, his soul gets a rematch with Azrael on the spiritual plane while his body heals. If he wins, his soul goes back to his body, and he always wins. By the end of "Logan Dies," this arrangement is actually undone, and the implication is that Wolverine's next death will be his last one, but we'll see whether or not that actually lasts.