Hey mark,
Wow that's quite the project you've got ahead of yourself.
My serious advice though is to definitely cut its proposed length down. The chances you have of getting an audience to sit through 1.5 hours of flash animation is incredibly limited...no matter how awesome it may be.
Personally, I'd say max 10-15 minutes man...and even that's pushing it.
It's your call, but that's just my 2cents