On an average day, there will be 4 hours of calls spread an hour or less apart for the first half of the day, with the potential for surprise calls for the rest of the day. The irony is that a lot of these calls are about why things aren't getting done.
The surprise calls are the worst. Even if I might have 2 hours of uninterupted time at the end of a day (when I am most tired and frustrated) it is impossible to get focused when there is always a looming threat of interruption. It's gotten so bad that I only get anything done late at night or over weekends, but then I am tired during weekdays and resentful that I had to throw away my freetime in order to move a project forward.