Five years is the maximum, and it is short enough that the ending should be chosen at the beginning. Initial approval for an established U.S. entity is generally up to three years, with extension to the ceiling; time spent physically outside the United States does not consume the limit in the same way.
Decide in year one what year five looks like
A commissioning assignment that starts as an eighteen-month project has a way of becoming the person's job. Priya and her employer should agree at the outset which of the plausible endings they are working toward: a return to the Lambton Shores operation with the American ranges running on local staff she has trained, a move into a different classification if her role becomes managerial in substance rather than name, or a permanent route begun with enough lead time to be realistic. Two practical timing points sit underneath that choice.
Knowledge transfer is itself the deliverable in most specialized-knowledge cases, and a petition that describes training successors is more coherent than one implying permanent irreplaceability. And any change to the placement pattern — more time at licensee sites than the petition described, or supervision drifting to the site owner — is a change that should be reviewed before it happens rather than at an extension.