Troy is absolutely right. From memory the average time an unprotected internet connected computer is safe before it gets targeted (port scans which then escalate into a pattern of attacks) is between 2 - 3 minutes (source - a major Australian Bank's IT research department - time taken to target a newly built server)!
If you never net connect nor insert any drives, program or DVD or USB material - well its inert and not exposed to new risks. But it carries all the bugs that weren't know when the software was originally delivered. An example of this is Apollo 11; when it flew to the moon there were 4 known non recoverable software bugs in the programs. Triggering one of these bugs would have killed the crew - so they were studiously avoided. A more thorough examination of the code a few decades afterwards revealed there was (memory fails me) somewhere between 90 to 200+ of these bugs; talk about thin ice!
So if you don't patch you carry all these faults.
BTW Colin - if you are I/O bound on your solid state drives - rather than RAID (stripe) them you might consider going to a REVO (PCI-express rather than SATA 2 or 3) attached SSD - these can give between double to triple the speed apparently of the SATA bus; so rather than 200 - 500 MB/sec you are looking at 700 - 1000 MB/sec ...
http://www.ocztechnology.com/ocz-rev...press-ssd.html