@Veera ,
Question 1. What is the maximum time users stay logged in?
It has no time limitation for this.
Question 2. How often users get automatically logout from Teams?
It has no such feature now. User should manually log out Teams client.
Question 3. Is there any option for users to stay logged in all the time?
It has no such option now.
The next best thing for your scenario is to inform users to manually sign out and re-sign in Teams client.
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.