Just some random thought.

When we see Lucrecia under the waterfall, she says she cannot easily die because of the Jenova cells in her.
Also, she seems just as young as thirty years before (not that those graphics show much, though.)
Furthermore, she speaks about "physical death" when referring to Sephiroth and herself, so we can perhaps assume she's not a ghost.

My question is, is Cloud bound to have a lifespan and /or a youth longer than normal, because of the Jenova cells implanted in him?