How to refresh credentials for Polly?

We're using aws-amplify for authentication. There's a helpful API called Auth.currentCredentials() which will return valid credentials generated by the attached identity pool.

I have this effect sitting in my root component:

```
/**
* refresh the AWS credentials
*/
useEffect( () => {
const THIRTY_MINUTES_MS = 1800000;
setInterval( async () => {
const [creds] = await Promise.all([Auth.currentCredentials()]);
const { accessKeyId, secretAccessKey, sessionToken } = creds;
AWS.config.credentials = new AWS.Credentials({
accessKeyId,
secretAccessKey,
sessionToken
})
}, THIRTY_MINUTES_MS);
}, []);
```

Even with this code, it appears that credentials are expiring after an hour. How can I refresh the AWS credentials for this library?

Thanks.