Normally 6-7 days.
One difference between African runners and European is that Africans start their activity without a coach, running in big groups where there is a top athlete.
For that reason, they start running fast (who can...), not having ideas about how to build their body for a long term project.
On the other side, this type of activity gives them great feeling with your body.
The task of a coach of African runners, therefore, is to teach them the physiological effects of different type of training on their body, giving to their individual sensibility the task to decide WHEN are ready for the next workout.
In my training phylosophy, when we start the SPECIFIC PERIOD (about 10-9 weeks before the Marathon) the athletes have to use some long (between 32 and 40 km) run, very fast (close to the Marathon Pace), and many times the same distances must be run with controlled variations inside (for example, 7+6+5+4+3+2+1 km at pace of 98%/99%/100%/101%/102%/103%/max possible speed, alternated with 1 km at 80% of Marathon Pace, and this training, being 34 kms, goes to replace a "classic" long run, progressive or even paced),
If the athletes are able running faster than my plan, I'm happy, but of course I have to "open" the recovery, because the physical effort was higher than the previews.
So, I give them "key workouts" they must use in succession, and they decide WHEN their body is ok for these workouts.
In other words, they don't follow a program, but the program follows them.
I prepare the key workouts on individual basis, and my plans never last longer than 2 weeks, because I need to prepare their key workouts looking at the REALITY of their situation, continuously updating the original plan.
For that reason, I'm against every type of microcycle for middle and long distances, especially during the special and specific periods.