You can get approximately 9 minutes of video per 1 Gigabyte of compact flash. This is for video encoded at the maximum bitrate of 15Mbps. If you reduce the bitrate to 10Mbps, then you can get 13 minutes of video per 1 Gigabyte.
Card Sizes:
4GB - 52 minutes of 10Mbps video
4GB - 36 minutes of 15Mbps video.
8GB - 104 minutes of 10Mbps video
8GB - 72 minutes of 15Mbps video
...
32GB- 416 minutes of 10Mbps video
32GB - 288 minutes of 16Mbps video
The largest compact flash card that has been tested is a 32GB compact flash card by Transcend. It can be found on Amazon.com here:
http://www.amazon.com/Transcend-TS32GCF133-133x-Compact-Flash/dp/B0012Q2PD6/
We also recommend Sandisk brand cards.