It depends on what you mean. Take a break from poker in general, or during a tournament or cash game? If during a tournament, then you need to take a short break: 1. If you feel that you have begun to play a game that is not your own; 2. tired and need to warm up; 3 visit the toilet)
You need to take a break from the tables when you are unlucky for a long time, you did not get enough sleep, if someone frayed your nerves or you are drunk, in these moments of life it is better not to play.
When you go on tilt and play to try to recoup your previous losses, including increasing the buy-in, it's time to take a break and review what you're doing wrong and correct it.
In person for a maximum of 3 hours, if you are not having a good day, much less, online every 2 hours I try to rest for 20 minutes I watch a comedy movie, in addition to the breaks. (that's in case you can't sign me in a tournament)
Goof afternoon.Every time I start feeling tiredit is the moment to stop my poker session and take a good break.After some hours, if feel fresh again,then I can play a couple of hours more.