CentOs 7 have a built-in configuration to close the inactive ssh session. In term of security it is a good thing but when killing a session after 1 minute of inactivity start to be a mess when you have multiple session opened in parallel.
This can be avoid on the client side by configuring a keep-alive period on the client side. To activate a such keepalive, you just have to connect with the following command line:
ssh -o ServerAliveInterval=5 firstname.lastname@example.org
This will configure client to send a NULL packet every 5 seconds to keep the session opened.