A big problem over ssh and especially sshfs is that your connection will often timeout and disconnect after inactivity.
To fix this you can modify the server but it may not be practical or you may not have access. Why not send keep alives fom your end (client side)?
Just edit /etc/ssh/ssh_config (not to be confused with sshd_config as that is the server side):
Find the line that says "Host *" and change it like this:
The first line means send a keep alive every 30 seconds (you can change it)
The second line means after 2 failures of keep alive, it will disconnect.