Thank you for your question.
The advantage of having professional services people coming in, in my line of business, is that it allows you, when the work is completed, to not have the person on board. So it's a quick response. Instead of gearing up your organization to the point where you have too many people for the work at hand, it allows you to get the job done, keep your core in place, and when the job is completed you can resume with the normal body of individuals you have.