When I shoot a three hour event, my nx5u file comes in at 30 gigs, so yours seems in the ball park.
Remember, in the olden days, minidv tape took up 13 gigs per hour.
When you say, comes in, do you mean the original m2ts file from the camera, or after it is converted to mac pro res?
Although I am not a mac person, I have heard there are more than one way to convert to the mac format, which will affect its size.
But size of file should not be your problem, just buy a bigger disk.
The more expensive problem is that editing the HD compressed as avchd takes a lot of computer power. Editing the SD, which the camera compresses as mpeg2, takes less computing power, although the file size will be about the same because it is compressed less than avchd.
John Lenihan
LeniCam Video Productions
http://www.lenicamvideoproductions.com