In my experience this is what happens with programmers in corporate environments and produces excessive hours - 2 hours concentrating in the morning, 2 hours concentrating in the evening, and 8 hours of bullshit in between.
Wow, 2 hours of concentrated work in the morning sounds exceptional to me. With open plan offices -- the norm in Brazil and Japan -- it's damn near impossible to have 20 straight minutes of uninterrupted work: phones ringing, people talking to each other from afar, people interrupting you, etc.
