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Yes, the belt will stretch over time. You get the best print quality when the belt tension is set correctly, not too loose or too tight, and this tensioner makes it much easier to adjust. Also, with the original configuration, tightening the x-belt will squeeze the z-axis rails toward each other which may cause binding. This tensioner eliminates that problem by putting the tension on the ends of the x-axis rods instead of the right z-axis bearing block. You can google for details on setting the correct belt tension.