Crashing is a process of expediting project schedule by compressing the total project duration. It is helpful when managers want to avoid incoming bad weather season. However, the downside is that more resources are needed to speed-up a part of a project, even if resources may be withdrawn from one facet of the project and used to speed-up the section that is lagging behind. Moreover, that may also depend on what slack is available in a non-critical activity, thus resources can be reassigned to critical project activity. Hence, utmost care should be taken to make sure that appropriate activities are being crashed and that diverted resources are not causing needless risk and project scope integrity.
Indeed, it is advisable to first crash activities early in the project as to have a leeway to crash other activities in the later stages of the project. Nonetheless, it is imperative that all project guidelines, resources and costs are diligently being tracked and are aligned to the aspirations of the client and senior managers.
[Editor Note: Please see this video I recorded on project crashing too. For coaching from me, check out Project Management Strategies That Work (And How To Implement Them)]