DP4 has a 2 GB limit last I checked, but I never made it to 4.5. I think I was at 4.01 or something when I used it.
while it does have the 2gb limit, each channel is its own seperate file, so you can run twice as long as compared to a recording program that only records "stereo" files
Even more to this however. Let's say you have a hard disk recorder that auto splits (or you manually split) files at around 2 GB. Each segment can be placed into DP on the same channel. What you have to be careful of is when you bounce the audio. If you bounce a 4 GB wave or SD file, DP will write it out that way, but you'll end up with a file that you can't use.
Typically what I do is put everything together in DP. Get my mix set correctly for the channels. Then save two copies of the project. Part 1 and Part 2. I delete the audio from part 1 that belongs in part 2 and then do the same in the part 2 project. This way I never have to worry about bouncing more than 2 GB worth of data.
Wayne