When the XNA Community Games were revealed back in November there were some quality titles that came out. However the standard trial version of any of the games had a strict time limit set into them - your demo could only last four minutes.

This left some games, such as Blow and In The Pit, with a less than desired trial limit. Blow has a long tutorial, and its more calm pace had some people not even finish the tutorial before time ran out. In The Pit specifically mentions in the tutorial that time will run out, and suggests you boot up the game again in order to get through it all.

Now things have loosened up a little - from right now all trial limits have been extended, you can now play the games for eight minutes before notified to buy the game.

Source: XNA Blog - Trial Mode Increasing From Four Minutes to Eight Minutes