Expires_in in client credentials grant type

Has as customize the claim expires_in of token returned in client credentials grant type?

Apparently I saw that the token always returns with a time duration of 1 hour:

{
  "access_token": "O2a8LusNuZfwQTW5mFfLI_k0tcxr2eJvZLwmXLbCHI0.wG-MWGI5AmNJYrmrMQpp5cY8xgEkIXpmeHjMD-qJkt4",
  "expires_in": 3599,
  "scope": "",
  "token_type": "bearer"
}

I was wondering if there is a custom shape with the same undefined mode as an api key.

No, an Access Token is not an API key.