Operating at extreme ranges requires highly skilled pilots to get the most out of their fuel. Just a few minutes of incorrect setting can make the difference between flying home and swimming home. Also, a large proportion of Japanese aircraft during the early part of the war did not have self sealing tanks. Therefore any bullet hole in a gas tank means you will start leaking fuel - if you don't have much reserve, this is a problem for you...
Given the lack of Japanese air-sea rescue efforts, operating at the extremes of range means a higher loss of aircrew, which OTL Japan could not sustain and IMHO absent major changes before the war as well as a much better flow of AVGAS to Japan after the war starts, they simply cannot fix.
Given the lack of Japanese air-sea rescue efforts, operating at the extremes of range means a higher loss of aircrew, which OTL Japan could not sustain and IMHO absent major changes before the war as well as a much better flow of AVGAS to Japan after the war starts, they simply cannot fix.