Most of our tournaments use synchronized breaks. The break starts at a set time, usually 55 minutes past the hour, and begins once the current hand is finished.
Some tournaments use a different system. In these, breaks happen 60 minutes after the event starts.
We use synchronized breaks so everyone can take a real break at the same time. This gives players a chance to step away from the computer for a few minutes.
In rebuy tournaments, the break can happen before the rebuy period ends. Add-ons might not be available during the break. They usually open when the rebuy period finishes. You can always check out the tournament lobby for details.