The current version of UAG has only been out for a few months at the time of this writing, but indeed we are aware of quite a few servers running previous versions that have been working for many years. In fact, some have been running smoothly for so long that when an issue comes up, no one within the entire organization even knows how the server LOOKS. We are not kidding... we have actually seen cases where a customer calls in and asks us what is that black box that's suddenly started ticking.
Beyond that, monitoring is not only good for solving problems. It allows the administrator to learn about the traffic patterns of his users, and to keep an eye on the server's performance over time. Usually, usage will increase, requiring a server upgrade at some point in the future and tracking activity is very important to be ahead in this game. Some people prefer to wait for the angry phone calls before starting to investigate the process and costs of an upgrade, but we'd like...