I can’t guess at all when the creator access token will be refreshed, sometimes a few minutes, sometimes a few hours.
The creator refresh token would be refreshing too. So I have no way to automatically get the new tokens from my application.
— Update: 2019-04-08 —
I found the reason is that my creator account logged in via oauth2 will refresh the creator token, causing the token in my application to be invalid.
There is an urgent need for a way to generate a creator token that will not expire or be refreshed.