There are some software limits, but I do not know what it is. It depends on whether you need the timeline or not, whether you need waveforms and thumbnails, and the number of tracks. Also, it depends on free memory, not just physical RAM. There are many variables. There is a numerical limit to a frame count that is used throughout: 2147483646. The maximum duration depends on the frame rate. At 60 fps that is 9942 hours. However, the timeline will have a problem well before you reach that.