Is this something that started recently?

connection closure can come from a number of different places.  Keepalives are mean to keep the connection 'hot' by periodically sending meaningless packets across the channel.  This can prevent some socket and routers from timing out and closing dead connections, but may not for example prevent a SHELL timeout due to shell inactivity.

Can you provide some more detail on what you're experiencing?  When disconnecting, do you have any visual clues as to why?