Been coding about 20yrs, In my case its not as much as the IQ but the ability to switch perspectives. I have seen that when I code or debug for long hours often I lose that critical ability and I often repeat the same mistakes. Eventually I take hours to accomplish what I would in 30mins, thats when its time to wrap up.

but I should point out that long stretches of time are different from quite (context switch free) streches of time.