Since a stereo recording usually runs about 1GB an hour, then a mono recording would run 0.5GB per hour. The file size limit for FAT32 (most SD cards are formatted FAT32) is 2GB, 2GB/.5=4hours. That's MAX!
If you record all eight channels into eight mono files, you can go 4 hours. If you link the channels in pairs into four stereo files the limit would be 2 hours. And that's what I hit running it once. It just stops, it does not start a new file like the H2 or many other recorders. That may be fixable with a firmware update.