Minimum 5 minutes after the first 30 minutes. That means get up and get away from the work area, stretch, do some edu-k or brain gym listen to a song or two.
At the very least 15 minutes after the 2nd 30 minute block. Longer is recommended.
If you work in 20 minute blocks. 5 minutes after the first block of 20 minutes 5 minutes after the second block of 20 minutes. At least 15 minutes after the third block. Longer is recommended.
I know you take more breas when working in 20 minute blocks however you might want to try it. People have reported that activation and studying is much easier in 20 minute blocks.
Alex
