DGEN campaigns do have a limit to how many of a certain aircraft etc are available and when that limit is reached no more of that item are available until the next resupply date.
These numbers are recorded in a file that you can edit. If you feel the campaign has given the Japanese too many spare aircraft just edit the config file.
Two provisos:
1. DGEN tracks supplies for entire theatre of the campaign not individual carriers or airfields
2, I am not sure if small stuff like AAA is tracked, it may just be always replaceable.
ALTERNATIVE:
Install the Lowengrin DCG instead
http://www.lowengrin.com/news.php