1 answer
Hi,
Great question. See bold below:
When using a monthly login-based license, a user consumes a login when signing in to a community. Already logged-in users don’t consume licenses when switching between their communities. Overages are calculated at the end of the year rather than on a monthly basis.
If users with a login-based community license access their communities through Salesforce1, they consume a login the first time they log in or if their session times out. A login is counted each time a login-based user authenticates to the community. Salesforce calculates logins from the LoginHistory table. The timeout period for a login is configurable up to a maximum of 12 hours.
More info here: https://help.salesforce.com/articleView?id=users_license_types_communities.htm&language=en_US&type=0
Best
