Hello JimMoz,
A MS Teams Meeting (Video & Audio), currently has a maximum capacity of 250 participants,
including internal and external attendees and I do not know the maximum duration length, however I have
been on a meeting for over 20 hours without disruption.
A MS Teams Live Event (Video & Audio) has a maximum capacity of 10,000 participant, including internal and external attendees and can last up to 4 hours. As of April 30, 2020 and to help during the COVID-19 crisis, MS did temporarily increase the max capacity
to 20,000 participants and a duration length of 16 hours. This will end on July 1, 2020
Below is a link to MS Teams Meetings and Teams Live Events that describes everything in great detail with specifications. I hope this helps.
https://docs.microsoft.com/en-us/microsoftteams/limits-specifications-teams
Regards,
Doug