We proved that the disposition of tandem fixed-beds of ZSM-5 with SAPO-18 catalysts could decrease the deactivation of the second catalytic bed during the methanol-to-olefin reaction. For this purpose, we prepared two catalysts based on ZSM-S zeolite and SAPO-18 zeotype; characterized them using XPS, XRD, Si-29 NMR, N-2 physisorption, NH3-TPD, and Fourier-transform infrared (FTIR); tested them individually, in mixed or tandem forms using a fixed-bed reactor or in situ reactors monitored with UV-vis or FTIR spectroscopies; and characterized the catalyst during the reaction or after it. The catalytic beds (mixed or tandem) did not offer any significant enhancement or synergetic effect in product selectivity. However, the catalytic lifetime of the second bed in the tandem catalytic beds (particularly if that is made up of the SAPO-18 catalyst) was prolonged because this bed receives less oxygenates (methanol and dimethyl ether) and more water, which slows down the deactivation of the second catalytic bed.