Unplanned change.

Unforeseen changes come in two forms: changes in people and
changes in operating environment. Each type represents a threat to
the ERP project.
Regarding people changes, take the case of a division whose general
manager is ERP-knowledgeable, enthusiastic, and leading the
implementation effort. Suppose this person is suddenly promoted to
the corporate office. The new general manager is an unknown entity.
That person’s reaction to ERP will have a major impact on the project’s
chances for success. He or she may not be supportive of ERP
(usually because of a lack of understanding), and the entire implementation
effort will be at risk.
Environmental change includes factors such as a sharp increase in
business (“We’re too busy to work on ERP”), a sharp decrease in
business (“We can’t afford ERP”), competitive pressures, new governmental
regulations, etc.
While such changes can certainly occur during a short project,
they’re much more likely to occur over a long, stretched-out time
period.
Schedule slippage.
In a major project like implementing ERP, it’s easy for schedules to
slip. If the enterprise software is being installed at the same time, software
installation deadlines might suggest pushing back the planning
portion of ERP. Throughout this book, we’ll discuss ways to minimize
slippage. For now, let us just point out an interesting phenomenon:
In many cases, tight, aggressive schedules are actually less
likely to slip than loose, casual, non-aggressive schedules.
Benefits.
Taking longer than necessary to implement defers realizing the benefits.
The lost-opportunity cost of only a one-month delay can, for
many companies, exceed $100,000. A one-year delay could easily
range into the millions. An aggressive implementation schedule, therefore,
is very desirable. But . . . is it practical? Yes, almost always. To understand
how, we ne ed to understand the conc ept of the thr ee knobs.