I'm considering recording raw video, no compression at 720p, 30 fps for 20-30 min. This woudl result in a file that is close to 80 Gbytes. I'm wondering what the maximum file size for importing into premiere Pro is and if I need to split this file up into smaller pieces. Any recommendations on how I may deal with uncompressed raw video that is pretty long in length?
There is bound to be some limit somewhere in the program, but you should be well below that. The biggest issue might be whether your computer is up to the task of handling it. If you will post your computer specs., someone will give you comments on that aspect.
Another option, might be to use one of the lossless CODEC's, such as Lagarith, or UT, instead of Uncompressed.
SMPTE 292M HD-SDI uncompressed 720p (RAW) is 1.485 Gbps, so 20 minutes would be around 223 GB. The best way to deal with those sizes is with lots of disk space and a good disk setup, meaning very fast transfer rates.