Long enough to obtain the slowest instrument. Regulator confirmations, credential evaluations and corrected employer letters each run on someone else’s schedule.
The external issuers set the timetable
Every item the applicant controls can be produced in a week; the items that decide the date are produced by other people. A professional regulator confirming a licence in good standing works to its own service standards. A credential evaluation agency needs transcripts, which the institution sends when it sends them. An employer letter that has to be redrafted by a firm’s general counsel can sit for a fortnight. Ask for each of these on the first day rather than in sequence, and record the date each request was made. Once those dates are known, the earliest defensible travel date follows arithmetically, and it can be communicated to the employer as a fact rather than negotiated as a preference.
Timing is driven by document readiness, intended start date, and the chosen admission or petition route. Build backwards from the proposed first workday and allow time to correct a letter, obtain an original credential, or resolve a name difference. Do not begin work merely because travel has been booked. A later amendment may be necessary if duties, employer, or work location changes materially. Hypothetical example: an audiologist receives a revised assignment after flights are purchased; comparing the new duties with the original professional listing determines whether the planned sequence remains supportable.