Cassettes are recorded as side A and side B. Two stereo pairs of tracks (four total) are available on a cassette tape; the first stereo pair is played or recorded when the tape is moving in one direction and the other pair when moving in the opposite direction. So a standard 60 minute tape can contain up to 30 minutes of recorded material on each side.
Prepare your audio tracks so that side A and side B are approximately equal in length so there is not too much silence on either side.
The current maximum length that can be produced is 84 minutes total.