Linux distributions do need to reboot on a regular basis to apply security patches.  In particular any kernel changes need a restart to take effect.<p>The last security advisory affecting the linux kernel for Debian was 5 days ago (<a href="https:&#x2F;&#x2F;www.debian.org&#x2F;security&#x2F;2015&#x2F;dsa-3426" rel="nofollow">https:&#x2F;&#x2F;www.debian.org&#x2F;security&#x2F;2015&#x2F;dsa-3426</a>).  There was another one about a month before that (<a href="https:&#x2F;&#x2F;www.debian.org&#x2F;security&#x2F;2015&#x2F;dsa-3426" rel="nofollow">https:&#x2F;&#x2F;www.debian.org&#x2F;security&#x2F;2015&#x2F;dsa-3426</a>).<p>Additionally because of the way shared libraries are loaded in Linux after you apply the patches you might have old, unpatched versions of (eg openssl) linked into currently running processes.  There are a few ways to handle this but a restart is one very simple one that is guaranteed to work.<p>Consequently any Linux machine that has more than about a month of uptime is probably missing patches.  500 days of uptime corresponds to a huge number of unpatched vulnerabilities.  So restarting is quite important and is unlikely to go away soon.