The maximum period in specialized-knowledge status is five years, and time already spent in the United States in that or a related category generally counts against it. An assignment should therefore be planned against the remaining balance rather than against a fresh five years.
Work out how much of the ceiling is already spent
Before the length of an assignment is agreed with a customer, the employee's own history should be reconstructed: previous American postings, their categories, and their dates. That balance, not the project plan, sets what is realistically available. Where the American entity is new, the first approval is one year and the extension is judged on what the company can show at the end of it, which shortens the useful runway further.
Planning also has to allow for the gap between a signed contract and an approval, and for the possibility of a request for evidence extending it. Hypothetical example: a greenhouse climate-software specialist is promised a four-year American project, having already spent two years in the United States on an earlier posting in the same category; the remaining balance will not cover the project, and the honest conversation belongs at the contract stage rather than at the third renewal. Where the remaining balance is short, splitting the work into a briefer posting supported remotely from Quebec is sometimes the honest answer rather than a workaround.