Before you move such large footage you should really try and figure out the actual size of it. Where ever it may be you should still be able to RIGHT CLICK IT and find out the SIZE OF IT by choosing either "GET INFO," "PROPERTIES," or "QUICK LOOK." Knowing the size from its original point would help you determine how much memory you will be using, needing and transfering. It would also let you know how long you will be waiting.
Personally the most I have imported into iMovie is around 5hr of footage as one movie. The only issue I found was that it took a while to import.