The maximum period in specialized-knowledge capacity is five years. If a move into a managerial or executive role is intended, it has to happen well before that limit, because an extension in the managerial category requires that the person has actually been performing those duties for a meaningful period before the petition is filed.
Plan the fifth year during the second
Five years passes quickly on a commissioning schedule, and the common mistake is to treat the limit as a problem for later. Two things are worth deciding early. The first is whether the intention is a temporary assignment followed by a return, in which case the plan is simply to manage the calendar and to keep records of any time spent outside the United States, since periods abroad can affect how the maximum is counted.
The second is whether the role is meant to become permanent, in which case someone should be examining an immigrant route years ahead rather than in the final months. A drift into supervising other technicians without any deliberate change of role is the worst of both: it neither preserves the specialized-knowledge case nor builds a managerial one. Decide which it is, and document it from the day it changes.