Question: I have many Linux servers (SUSE 9 &10) used to run web services that provide data to large calculation grids. Recently we have had some difficult to explain outages (i.e. hardware and software logs are not showing any obvious errors) and we are starting to wonder whether the long uptime (typically 200-300 days) is the issue. Given that these servers are heavily utilised, should I consider a regular reboot cycle?

Answer: 
I actually reboot my servers on a fairly regular basis, any time major configuration changes are made. It's important to know that in the event of an emergency the server software will come up without a hassle. The last thing you want is to be in a position where you are trying to recover from an outage but are having to mess with your server configuration because you didn't thoroughly test it when you set it up.
You can additionally wrote some scripts which will check (as much as is possible), if the current state of your machine, is going to be the state of the machine post-reboot.

What I mean by this is...

* `/etc/init.d/*`
	+ Check that all services currently running, are flagged to start on boot
	+ Check that all services not running are flagged not to start on boot
* `/etc/fstab`
	+ Check that all mounted filesystems (i.e. `/etc/mtab`) have a corresponding entry in `/etc/fstab`
	+ Check that all filesystems specified to be mounted on boot in `/etc/fstab` are also currently mounted.

This is of course not a complete check by any means, but it does reduce the risk of troubles post-reboot.

Additional to this, you should (imo) set a policy for server package updates, in some sensible order, say 1 group per week...

* Crash & Burn Servers
* Development Servers, Training Servers
* Test Servers
* Pre-Production Servers
* Production Servers

Also have an overall plan, such as "All servers will go through a complete OS upgrade once every 6 months".