That’s a lot of media. Factors that will slow it down are the kinds of media, the amount of metadata and the performance specs of the hard drives the media is stored on. Also make sure you’re on the latest OX/FCPX as they have upped the performance for very large projects.
Noah
FCPWORKS – FCPX Workflow
FCP Exchange – FCPX Workshops
XinTwo – FCPX Training