The principal's L-1B eligibility ends at five years, and derivative status ends with it because dependants hold status only through the principal. Anyone who intends to stay needs a different basis before that date, and the planning has to start years earlier.
The ceiling arrives on schedule for everyone
Families experience the limit as a surprise even though the date was knowable from the first approval. Spouses and unmarried children under twenty-one hold L-2 status derived from the principal, and derived status has no independent life: when the principal's period ends, theirs ends. An L-2 spouse's employment authorisation, which exists incident to that status, ends at the same moment.
Hypothetical example: a household from Saint-Joachim-de-Shefford reaches month fifty-four with a spouse running a growing bookkeeping practice and a child two years into a U.S. high school, and only then asks what happens next. The options that exist are all slower than the time remaining.
Some paths lead onward and each has its own gate: a change to another employment category, a switch to L-1A where the duties genuinely became managerial and the seven-year ceiling applies instead, an employment-based immigrant petition begun early enough to matter, or a period spent outside the United States before returning. None of them can be started in the last quarter and finished in time.