The timeout is configurable.

It's configurable, but outside of having an IAM users with long-term IAM credentials (which is not ideal security-wise), sessions can be max 12 hours long.

No. You could either set it up with SSH or HTTPS credentials (managed via IAM Console or CLI) or use the AWS CLI's credential helper that managed everything automatically. The credential helper was a little weird to set up the first time I used it, but once I wrote up the instructions it was easy enough.

Honestly I've never come across the '12 hours of usage' thing for AWS. But I only use CodeCommit, EC2, S3, SNS, SES, and other low-level services.

The "12 hours" comes from IAM roles... some organizations don't allow folks to use IAM users for security reasons; many are now swapping to a setup like IAM Identity Center where they are granted temporary AWS credentials for an IAM role using an SSO provider.