geothorn,
In general we'll stay depending on the severity of the storm, how close it will come to us, and how long it will linger. Last year we stayed for Frances which was a sloooooow moving Cat 2, and it sucked, so we left for Cat 3 Jeanne two weeks later. If a Cat 4 or 5 is coming close, don't plan on stopping by to visit.
As for packing up stuff, once you get your mind right and realize that your house and possessions are only temporarily yours, locking up and leaving isn't such a big deal, and it's far better than being recovered (not rescued) by a FEMA USAR Team.
You can Alamo up against invading armies and looters, but you can't hold the roof decking on in the face of 180mph winds, or hold the walls together in front of a storm surge.