So if I were to buy an 80 GB Intel SSD and use it an for an OS drive, how long do you guys think it would last before croaking? When I say "croaking," let's assume I mean that the usable capacity has dipped below 40 GB.
Croaking would imply to me a complete hardware failure to becoming a brick, or at a minimum, having become as slow or slower than a mechanical drive.
But if we want to use your definition of croaking, I can get you more exact figures when I get home (to my SSD). Until then, figure you have the OS, you'll have your documents/files/pictures, which I assume are not a particularly large folder (since you have a server). Beyond that, my 60GB allows me to have four to five large programs or games; i.e. UT3, SC2, about 60% of Adobe CS4 Suite, and Solidworks, with still a few GB spare.
There's nothing really wrong with running an SSD a little low on free space; at least, I haven't seen anything wrong. Between Windows 7's memory management, the SSD's speed, and 6 GB of RAM, it's never given me a problem.