Flying domestic U.S. routes you are in continuous radar contact; speaking on VHF radio; and certainly not crossing any FIR boundaries. If flying an FMS equipped aircraft that leaves lots of time to concentrate on the expanded airman's information manual and other publications that pertain to safety of flight
I can see how you might think that would be boring if done 7+ hours.
As NF said, that isn't necessarily the case with international flying. Spending 45 minutes trying to get a hold of Bombay Radio on HF or close to an hour transiting the Amman, Damuscus, Nicosia, Ercan corridor tends to keep one busy. Couple that with reviewing information on airport's that you only go into a few times per year; keeping track of position reports; fuel monitoring; thundertorm avoidance; etc keeps one pretty busy. Sometimes it is amazing how fast 7 hours goes by.
Typhoonpilot