Perpetual SSH connnection security and practical implications

I have used the linux desktop for many years, but I rarely get into its networking aspects. I run a personal fileserver (primarily running owncloud on Ubuntu 14.04), and to perform regular maintainence and log-checking I ssh into the machine. I find myself leaving a ssh connection open from my desktop to the fileserver from time-to-time, simply out of convienince.

My question is two fold:

1. 
   

   {What are} / {are there} security implications of leaving a ssh connection perpetually open?

   
   


2. 
   

   {What are} / {are there} practicality implications? I.e. network usage, etc...

   
   

   I realize that from the traffic viewpoint, there will be an occasional 'keep alive' packet to maintain the connection, but otherwise I don't expect much overhead. Correct?