Changes in the environment mean that the forecasts often have to be changed. Along with these, the related plans may well also need to be changed. Continuous monitoring of performance, against predetermined targets, represents a most important aspect of this. However, perhaps even more important is the enforced discipline of a regular formal review. Again, as with forecasts, in many cases the best (most realistic) planning cycle will revolve around a quarterly review. Best of all, at least in terms of the quantifiable aspects of the plans, if not the wealth of backing detail, is probably a quarterly rolling review — planning one full year ahead each new quarter. Of course, this does absorb more planning resource; but it also ensures that the plans embody the latest information, and — with attention focused on them so regularly — forces both the plans and their implementation to be realistic.