I just wanted to offer some suggestions.
Make sure to factor in the actual amount of time you can actually spend in your break.
What I mean is your ideal schedule of 5 minutes between each block may not be so easy to manage. At least that's how I found it. The problem is it can take 2 sometimes, 2.5 minutes to go thru the security check (metal detector, pulling up sleeves, finger prints etc).
Oh and don't wear pockets! My friend warned me of this- because then you would have to let them check your pockets too everytime you come back -- which would waste more time!!
During my first break I went to the bathroom, had some water, an then went through the check, got back an entered my CIN. I think 8 or 9 minutes had passed!!!
The next two blocks I took breaks but remained sitting at my station.
I took a long break for lunch when I had 1 block left. Before that I went out briefly, stayed near the lockers, had a snack, some water, and went back in. I didn't go out. My most feared scenario was running out of break time and having my block time get cut short!!