How long can QT record the audio and video on the screen before automatically shutting off?

There's going to be a live video stream very soon and I *really* want to record it. I know QT can record the audio and video of what you have on the screen, but I need to know how long it will record before automatically shutting off. I don't want to be right in the middle of the video and I lose the recording 😟 lol