I've noticed that my ssh-agent process seems to stop working with 'ssh-add' after a few days
or so. Issuing 'ssh-add' from an xfce4-terminal results in the error message

"Could not open a connection to your authentication agent."

Why is this? There seems to be a myriad of ssh-agent processes running.
Is there a standard way to restart ssh-agent? I belive killing process
27850 will dump by Xsession from previous experience.

mylo    2594     1  0 Sep05 ?        00:00:00 ssh-agent
mylo    2614     1  0 Sep05 ?        00:00:00 ssh-agent
mylo    2629     1  0 Sep05 ?        00:00:00 ssh-agent
mylo    2641     1  0 Sep05 ?        00:00:00 ssh-agent
mylo    2659     1  0 Sep05 ?        00:00:00 ssh-agent
mylo   10768     1  0 Aug24 ?        00:00:00 /usr/bin/ssh-agent -s
mylo   12904     1  0 Sep08 ?        00:00:00 ssh-agent
mylo   13036     1  0 Sep08 ?        00:00:00 ssh-agent
mylo   13292     1  0 Aug24 ?        00:00:00 /usr/bin/ssh-agent -s
mylo   13473     1  0 Sep02 ?        00:00:00 ssh-agent -s
mylo   13907 19346  0 19:41 pts/5    00:00:00 grep ssh-agent
mylo   27850 27796  0 Aug25 ?        00:00:06 /usr/bin/ssh-agent /usr/bin/dbus-launch --exit-with-session /bin/bash /home/mylo/.xsession
mylo   27891     1  0 Aug25 ?        00:00:00 /usr/bin/ssh-agent -s
mylo   29792     1  0 Sep01 ?        00:00:00 ssh-agent
mylo   30159     1  0 Sep11 ?        00:00:00 ssh-agent