You are limited only by the space on your hard drive.
You are asked in the setup window for creating a new song how long you want your song to be. The default is 5:00 minutes.
You can change it once your session is already open though, you can change it in your Song Setup found in the options menu.
To get to Song setup:
- Windows - (Control + , ) - hold Control and hit the comma
- Mac - (Command + , ) - hold Command and hit the comma
When Setting page comes up at the bottom click "Song Setup" (see picture below)
Then change your time base from Bars to Seconds.
Then you can change your end time to whatever you want.
Keep in mind that if you run out of hard drive space, the recording will end.