Yes, but how does Aerith's death effect the length of the game? With the way it deeply effects each main character, their reactions, etc... if Aerith had originally been meant to live, they'd have to do A LOT of changes to pull that off, and it'd have taken far longer. Not to mention all the things the others in this thread have already mentioned. The only rumor involved in this is that it was supposed to have been possible to revive Aerith (edit: meaning the rumor was that they were going to include this sidequest, but scrapped it because they were short for time), which is the closest thing that would make sense, though the rumor is most likely b.s.

I never liked her though, so my opinions on all this are rather biased.