AWS IAM role expiry

Question

On expiry of IAM roles:

• What is the logic for IAM roles to expire, when you need them for longer. I really cannot see it.
• How do you when processing, get the an extension of the IAM role without some serious failure?
  • I did the IAM course but felt that was not well addressed.
  • E.g. a long running AWS EMR Spark data pipeline on a massive scale for cross account access?
    • If the Spark data pipeline has finished the Stage of reading from S3 and that role expires, may be that does not matter if you do not save subsequently to S3.