Ever since we announced our intention to disable Basic Authentication in Exchange Online we said that we would add Modern Auth (OAuth 2.0) support for the IMAP, POP and SMTP AUTH protocols.
Today,...
Updated Jun 30, 2022
Version 6.0
Blog Post
1 MIN READ
Announcing OAuth 2.0 support for IMAP and SMTP AUTH protocols in Exchange Online
https://github.com/AzureAD/microsoft-identity-web/wiki/token-cache-serialization
I think the answer is on that page. Essentially the token cache expiration is up to the application /developers and it should be set to something higher than the refresh token lifetime in Azure AD. The refresh token lifetime is by default 90 days but can be different based on Conditional Access policies applied to the user, and previously could be controlled at the tenant-wide level. So it's tough to know the lifetime without having access to the Azure AD admins to get the info from them.
Hope this helps. I'm subscribed to this thread and thought I'd take a stab at this one.