I've found it best to use a three-stage model for most of these kinds of projects. Stage one is the things that we think we can do within six months given our available budget and other time commitments.
Stage two extends out to eighteen months. That's the period of time in which we want to complete the basics of almost any initiative. In my experience, extending projects beyond the eighteen-month point almost always assures that they either keep changing or never get done or both.
Finally, I find it helpful to describe the ideal for our initiative. If we had unlimited resources, what would we do? That's Stage 3 -- the Ideal Stage.
I've found that the rapid development of net/web technology many items that we thought would need to go into Stage Two wind up as possible in the first six months. Many of the things that required special programming (and were therefore in the Ideal area) become available as off-the-shelf.
