I am subcontractor on a large commercial project, and the project is taking longer than expected. We are still providing labor and materials for upcoming completion, and have been fully paid up to this point and time.
Last furnishing date is generally not a required piece of information for a Florida Notice to Owner ("NTO"). So, while it may be included in some formats to provide a clearer picture of the work being done by the sender, it generally shouldn't impact a notice's viability.
Of course, the last furnishing date will affect the FL mechanics lien deadline for the project since that deadline is 90 days after last furnishing labor or materials to the project.
For a breakdown on the Florida NTO requirements, this article will help: What information must be provided in the Florida NTO?