Derivative L-2 status ends when the principal's L-1B status ends, so the spouse's employment authorization and the children's dependent status stop at the same time. Planning for that date has to begin years earlier, because the family has no independent claim to remain.
One expiry date governs everyone
The five-year ceiling is the household's ceiling. When Anneke reaches it, her spouse's right to work, which existed incident to L-2 status rather than through a permit, expires with her status, and any dependent child in L-2 loses that status on the same day. Three planning points follow.
Days spent outside the United States during the assignment can be recaptured with travel records, which sometimes buys several months but requires the records to have been kept contemporaneously. Eligibility for a fresh L period generally requires a year of qualifying employment abroad, so a return to Ontario is a reset rather than a defeat. And any family member with an independent claim should develop it well before the deadline, whether that is a spouse with an employer willing to petition, a child accepted to study in their own right, or an immigrant petition begun early enough to matter.
Children in L-2 may study throughout but may not work at any age.