GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
That's a good question and unfortunately, I am far from being a source of information on the Japanese military's proceedure regarding pilot rotation.I wonder if some of that time might have been recovering from wounds received in battle or aircraft mishaps? Not disputing what you said in any way, but maybe after recovering, they were sent to an OTU in order to get their feet wet again?
However, I do know that Saburo Sakai spent a year as an instructer after recovering from his wounds he received from an SBD's rear gunner.
Then there was also the case of the Tainan Air Group (which Sakai had been assigned when injured) were rotated home to replace personnel, the ten original pilots of the group were assigned to instructor positions.
So it seems that the Japanese did rotate experienced pilots during the war - at least until their situation became dire.