Eight weeks may or may not be workable; it depends on the evidence, the filing route and current adjudication. Premium processing shortens USCIS adjudication but does not replace preparation or guarantee approval, and the customer's deadline does not change the legal standard. Confirm the applicable process and current timing before promising an onsite date.
Tell the customer what depends on which approval
Separate the work the employer controls from the government process. The employer controls how quickly it gathers the document index, technical narrative, payroll records and ownership evidence; do not assign an invented two-to-three-week duration. Premium processing shortens USCIS adjudication to its current official period, but a request for evidence can suspend that clock without a predictable one-month addition.
An eligible Canadian L applicant may use an approved petition or an applicable designated port-of-entry Form I-129 procedure, so confirm the current route. The customer contract should make the onsite date conditional on immigration approval, with a remote-support alternative. Do not let the technician enter as a visitor to begin work early.