Post-production is always the killer on projects like this. The Phase II guys can testify to that, as they're experienced with it. Once everyone's on-set and shooting you make rapid progress, but the stuff that has to happen after is, in a way, the bigger job, because it's a smaller number of people with a bunch of BIG tasks: editing, color-correction, ADR, foley, sound effects, scoring, visual effects, etc. If you can make it your full-time job it goes pretty fast. If you're all-volunteer, any hiccup or delay in the chain can affect the whole thing.