Well, its been hinted at in several fics, I thought I'd go ahead and hit the bugger head on. *shrugs* Its not great, but it doesn't suck either, so... *sheepish grin*
Cloud could never understand why someone would want to live forever. He was, after all, immortal, and he rather thought it sucked. You'd think after losing friend after friend, lover after lover, he'd learn not to open his heart to anyone. That didn't stop it from happening again and again, though. He thought time and again that he should stop doing this to himself, stop opening himself to the horrible pain that always came when someone he loved died, but every time he thought he'd decided he wouldn't let it happen again, he'd find someone else who made him laugh, or smile, someone he could lean on when the world hurt him too much, someone who needed him in return. And each time he found that person, he let them in. After all, what was the use of being alive if you didn't live? Life was happiness, but life was pain too. You couldn't have one without the other. So the world would continue on, and people he knew lived and died, and he held on to the happiness that came from having known and loved them, and embraced the pain that came from having known them and lost them, because as long as he felt that pain, he knew he was still living. He'd seen what became of people who closed everything out, pain and love, and he didn't want to become like them. People who refused to live turned into monsters and Cloud wouldn't become what he hated the most.
...Still, he couldn't help but be puzzled by those who sought long life. After all, didn't they realize that while they might live, everyone else would die?