System administrators that took all this advice to heart and did their best to follow it would be fantastic system administrators -- for a day. Eventually, the environment will change, and one day our fantastic administrator would be caught flat-footed. The reason? Our fantastic administrator failed to plan ahead.
Certainly no one can predict the future with 100% accuracy. However, with a bit of awareness it is easy to read the signs of many changes:
An offhand mention of a new project gearing up during that boring weekly staff meeting is a sure sign that you will likely need to support new users in the near future
Talk of an impending acquisition means that you may end up being responsible for new (and possibly incompatible) systems in one or more remote locations
Being able to read these signs (and to respond effectively to them) makes life easier for you and your users.