Handling Refresh Tokens

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I'm getting started using the SDK to interact with a Personal OneDrive account. What I've established so far from testing is that I cannot use Application Permissions with Personal OneDrive (please correct if I'm wrong though), so I must use Delegated Permissions (as you need a user context which doesn't exist in an Application Permission).

The SDK documentation says

Microsoft Graph PowerShell automatically refreshes the access token for you and sign-in persists across PowerShell sessions because Microsoft Graph PowerShell securely caches the token.

I can't find much specific detail on this though. Are there any time limits on how long the access token will be refreshed for? What is the recommended way to gracefully handle an expired token if there's been a problem? As I would like the script to run unattended / scheduled, I need a way to alert if it is waiting on the user to manually re-authenticate.

Does granting the "offline_access" scope have any extra benefit if using Connect-MgGraph?