Your IT has set up Conditional Access policies with a Sign-in Frequency set too low (it should really be labeled as a period, because it defines the time period that will occur before reauthentication is required). For regular users like all of you, forcing reauthentication that many times each day is excessive and just cruel on the users. They maybe thought it would make them super secure, but it only trains the users that MFA is an annoyance rather than an important security feature.

It’s a setting that can easily be changed, so make some noise and see if you can get some feedback passed through your org structure to IT.

Yep. I sign in once when the app is opened (which happens automatically as I’m logged into the computer as my Entra ID) and then am never prompted again until I close and reopen Teams.

Something is misconfigured in the environment, or there is a security policy that is set way too high, or one is scoped incorrectly. It is definitely not the normal or expected user experience.

Teams has a lot of faults, but that one is on your org’s admins and security team. Hopefully for you it’s a mistake and not done intentionally.

I've worked at different places that used Teams, and that thing with having to re- login regularly is certainly fault of whoever administers Teams within your organization.