While long-term, embedded coaching is not encouraged, most organizations can benefit from some period of coaching once their teams are trained and they begin moving toward an Agile way of working. This can be a couple of months of regular presence at organizational locations, then changing to less frequent physical presence (i.e., video conference calls).
The length and depth of this coaching will, as expected, depend a great deal on the size of the organization, the physical distribution of team members, and management's ability to engage in the organization's transformation.
Coaching can occur at the team and/or management level depending on the needs of the organization.
Any organizational transformation effort, besides training and planning, should expect a lengthier period of coaching to be a part of the transformation effort.
One key goal of any such coaching would be to develop, within the organization itself, an internal coaching capability.