That depends on how quickly records are gathered and how many open questions the reviewer finds, so agree on milestones rather than a date. The published material describes vetting in terms of weeks, but that is a description and not a promise, and later stages depend on visa availability and any interview.
Set review checkpoints before commitments
Fix dates for the eligibility opinion, the completed document inventory, and the decision on whether to proceed. Keep resignations, property sales and school enrolments behind those checkpoints. Ask the adviser how they will notify the household if something in the file changes the assessment.
Anyone offering a guaranteed completion date is describing something the published process does not support, since government review, visa availability and possible additional document requests are outside an adviser's control. Hypothetical example: a household changes advisers midway through preparation and discovers the document inventory was never written down, only discussed. A first review would have agreed at the outset who holds the file, how updates are recorded and what the deliverable actually is, so that the work already paid for remains usable by whoever takes over.
Fix dates for the eligibility opinion, the completed inventory and the decision itself, and keep resignations, property sales and school enrolments behind those checkpoints rather than beside them.