It doesn't have to be "off the grid" in the literal sense, although it helps to divorce one from the electronic tether back to the office, but unplugging from the daily info stream is an important part of my mental processing.
I've found my productivity has bumped up a notch simply by turning off email notification. The steady "Ping" was enough to drag my workflow down during the day, while simply checking in once I've finished the task of the moment is quick enough to satisfy everyone on the other end of the email. One or two hours of steady focus is drives far more value than instant response to queries.
In a similar way, turning off the electronics for a day or two and doing anything else- a nice walk, a chapter of that 500 page book you've been working on, a chat with your spouse- brings more focus to the job wen you return on Monday than stringing it out mentally all weekend.
Summer is a good time to develop the unplugging habit. Start tonight.