Secretly teach you a good way to get free tokens:

When your Codex quota is relatively small but you still have a lot of work, you can have it split the task into several parts and open multiple windows to work on them simultaneously.
Because Codex is really considerate, it doesn't stop the task just because the quota is exhausted; instead, it keeps working until the task is completed.
As long as you don't hit the context capacity limit, you can get a lot of tokens for free.