With experience in both, it really depends on your situation...sometimes even "all or nothing" environment is not good, as each platform has pros/cons to it. There are other considerations as well...typically, a migration to Novell means you do notneed as much hardware. In other situations, you need have dependent applications that require a Windows server.
It's hard to say without more information. Netware is not just file/print, but now includes MySQL, apache, php support, iPrint, iFolder (secure data replication) and of course, resource access is based on Directory Services.
Another point...are you a dedicated IT resource or is it a part of your job? If you are dedicated, then a stable environment would easily allow you to then address issues like desktop mgmt (via Zenworks for Novell) and other areas of interest. Or, it would allow you to do other things for the company.
I've seen several Novell servers run for more than a year without a reboot in small offices. In a Windows environment, if it made it that long, it would still signify that the server was severely under-patched and probably vulernable. But again, questions about connectivity, exposure, etc., come into play.
The guy who replied that a too-stable environment could adversely affect job stability is off the mark. The past few years, folks paid by the hour had a vested interest in providing unstable solutions, but as the market has turned, you are beginning to see that change.
Dave