Extended mirror symmetry is a conjectured relationship between open Gromov--Witten invariants for Lagrangians in Calabi--Yau threefolds and period integrals associated to objects in the derived category of the mirror. I will discuss work in progress on understanding this conjecture for lines in the mirror quintic threefold. I will construct the Lagrangians in the quintic that correspond to these lines using techniques inspired by the SYZ conjecture, and explain how to recover predictions of Jockers, Morrison, and Walcher about the limiting value of the open Gromov--Witten superpotential for these Lagrangians.