Hey there! This is a good question, so I hope this answers properly:
1. The Judges will play your entry for a minimum of 20 minutes. If the game completes (back to Title screen, for example) before 20 minutes, they'll likely DQ it.
2. The Judges will stop playing your game at the 1 hour mark, regardless of how far along they are, and likely won't consider anything beyond it. Some of the judges have said as much on stream.
Hopefully, that gives you a metric of what will be used to judge your game. :-)