The finite partial translation symmetry apparent in array antennas can be exploited for effective calculation of the Method of Moments (MoM) impedance matrix. With a geometrical array decomposition built on nine subdomain components, the obtained MoM impedance matrix inherits a partial block Toeplitz structure, which enables fast calculation time and reduces memory allocation. In this paper, we further improve the calculation time by reusing already calculated submatrices of the MoM impedance matrix. By identifying corresponding elements between the nine components, already calculated submatrices can be extracted to create submatrices previously deemed as necessary to calculate. The reusing strategy reduces the number of submatrix calculations to perform from O(NxNy) to O(Nx+Ny), of a part of the impedance matrix, for an Nx×Ny array.