9 bars usually, but don't get me wrong..i don't make 9 bars of beat progressions. 9 bars are actually reserved for other sounds to interact with eachother.
Drop the idea of becoming someone else, because you are already a masterpiece.
with ableton has awesome flexibility, sometimes i program quarter note loops and then as i'm track building I continuously expand them to 1/2 , 1 , 2, 4, then 8 bars.
This way I'm not investing a lot of time into stuff I'm not necessarily going to use.