Avoid decisions that assume a fixed end date. Scope changes can shorten an assignment as easily as extend it, and an extension is not automatic. Eligible spouses and unmarried children under twenty-one may seek dependent status, and a spouse in valid L-2S status is employment-authorized incident to that status.
Keep the reversible options open
Renting rather than buying, and timing school enrolment to full terms, cost something and buy flexibility that a shifting project makes valuable. Where a partner is arranging employment, they should understand that their own authorization is tied to the principal's status, so a change affecting the principal reaches the whole household. Review the family plan when the assignment's scope changes materially, not only when it ends.
One condition should be understood by the whole household rather than only by the principal. Dependent status extends to a spouse and unmarried children under twenty-one; a spouse in valid L-2S status is generally employment authorized incident to that status, and children are not work authorized by it. Because that authorization is derivative, anything that affects the principal's status reaches the spouse's job as well.
Where a partner is weighing an offer, it is worth their asking the employer how a change in the principal's assignment would be handled, before rather than after accepting.