Does a pro maintain laser-like concentration during his entire round? No way. Not even Jack Nicklaus keeps the focus for four straight hours - at least not without taking a few breaks.
As I walk between shots, I let my mind wander to all sorts of non-golf things - to my kids, to my next fishing trip, or whatever - but when I'm playing my best, my mind clicks back into focus well before I reach the ball.
At a point about 40 yards short of the ball I begin to analyze the situation that's facing me. I look at the tops of the trees to check the wind, I look at the pitch and roll of the green area to get an initial feel for the way the ball will roll, and I look at the people around the green to get depth perception. By the time I get to my ball, I'm fully focused on the shot.
Some of my colleagues on Tour delay this type of thinking until they arrive at the ball. I'm not saying they're wrong, but I do recommend my method to all amateurs, and for one big reason - it will speed up play!