There's no standard timeline, since it depends entirely on which route fits the spouse's circumstances, if any does. This can range from a straightforward process to one that takes considerably longer than the principal's TN case, so plan the move without assuming the two align.
Don't tie the move date to the spouse's status
Set the household's relocation timing around the principal's confirmed TN plans, and treat the spouse's work authorization, if pursued, as a separate track that may finish earlier, later, or not fit at all. Build in a realistic period where the spouse isn't yet authorized to work, and revisit the plan with counsel once more is known about which route applies. Start the spouse's assessment first where the household's finances depend on the second income, because it is the longer and less predictable of the two enquiries and it may return an answer that changes the whole plan.
That ordering feels counter-intuitive when the principal has an offer and a start date, but the principal's route is generally the better understood of the two. Build the household budget on one income for a period longer than anyone expects, and set a review point at which the family reassesses if the spouse's position has not resolved, rather than letting the question drift.